OK, thanks Gary.
However, it's the total strength which is the product of the number of units and their average strength, that really matters. Since the number of divisions was great, the total strength was impressive too.
Actually, they are also impressive on a division-by-division basis, because they translate into quite high combat strengths - if the FHO rule of thumb values are used, to something around 5,500 men or more per division, in almost all cases.
This was considerably better than can usually be found on the German side, at almost any stage of the war. For example, on 31 October 1943, not one of AOK 2's divisions had a Gef.st. exceeding 3,000 men. On 13 December 1942, two of AOK 9's 27 divisions had a GefSt of more than 3,000. On 3 October the same year, the average Gef.St of that army's divisions were 2,240 men. Some divisions had reported only partially which understates the average, but it must certainly have been well below 3,000. On 4 July 1943, the average Gefst was roughly 3,100 men. On 23 January 44, it was 1,468 men. These (AOK 9) are Infanteristische Gefechtsstärke (includes only the Gren.Btl., Pi.Btl. and Schnelle Btl/Aufkl.Abt - not the artillery Rgt).
However, these (except where marked) are full GefSt.:
23.10.42, AOK 11: 5,833
5.4.44, AOK 17: 3,235 (Inf.)
20.10.42, AOK 17: 4,363
15.7.44, AOK 18: 5,655
26.8.44, AOK 18: 4,285
7.6.43, AOK 18: 5,651
Same, but just Inf:: 3,001
You have to go back to the first year of the war to find significantly higher figures. For example, on 17 January 1942, 21 of HG Süd's divisions reported a Gefst of at least 7,000, some had as many as 10,000. Only 7 had fewer than 5,000. But these were of course still divisions with 11 infantry batallions (incl the Pi. and AA btl), plus a 4-batallion Artillery Regiment.
Hence, in terms of combat manpower, Soviet divisions even at 6-7,000 men overall strength were strong compared to what was usually the case on the German side, despite the overall considerably larger size of German divisions. In fact, if we disregard the artillery (which made up a large proportion of German divisional GefSt, but much less of that of a Red Army Rifle Division) I don't have a single data set from later than early 1942 that implies Infantry strengths on the same level as that possessed by the Soviet Armies quoted here.
This illustrates the impact of the fundamental differences in divisional structure between the two armies, if one wants to compare divisional strengths. The point is further borne out by the figures of non-combat Front troops, who are, relatively speaking, much higher than the fairly paltry number of (non-combat) Armeetruppen in a German AOK. In addition, the non-divisional combat units in these Fronts also seem to have been very numerous compared to the amount of fechtende Heerestruppen normally found with an AOK.