I found this perfect number and thought it was rediculously long! Got me thinking, what is the largest known perfect number and how many digits is it?

541625262843658474126544653743913161408564905390316957846039208183872069941585348591989999210567

1992191905739008026364615928001382760543974626278890305730344550582702839513947520776904492443149

4861729435113126280837904930462740681717960465867348720992572190569465545299629919823431031092624

2444635477896354414813917198164416055867880921478866773213987566616247145517269643022175542817842

5481731961195165985555357393778892340514622232450671597919375737282086087821432205222758453755289

7476256179395176624426314480313446935085203657584798247536021172880403783048602873621259313789994

9003366739415037472249669840282408060421086900776703952592318946662736152127756035357647079522501

73858305171028603021234896647851363949928904973292145107505979911456221519899345764984291328

(Note:This is ONE number, but due to the length I had to write it in several lines.)

Similarly to a perfect number, we have an almost perfect number which is a natural number n, such that the sum of all divisors of n [ σ(n) ] is equal to 2n - 1. The only known odd almost perfect number is 1. This is interesting, since an almost perfect number can be odd, while an odd perfect number has yet to be found! The only even almost perfect numbers known are those of the form 2k for some natural number k. However, it has not been shown that all almost perfect numbers are of this form. Which is interesting, since so much time was spent trying to find the form of perfect numbers, yet there is no known form of an almost perfect number—-yet.