851205521664 has 405 divisors, whose sum is σ = 2616097001133. Its totient is φ = 275276703744.

The previous prime is 851205521549. The next prime is 851205521669. The reversal of 851205521664 is 466125502158.

The square root of 851205521664 is 922608.

It is a perfect power (a square), and thus also a powerful number.

851205521664 is a `hidden beast` number, since 8 + 5 + 1 + 20 + 552 + 16 + 64 = 666.

It can be written as a sum of positive squares in only one way, i.e., 99724587264 + 751480934400 = 315792^2 + 866880^2 .

It is a super-2 number, since 2×851205521664² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (851205521669) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 5712788662 + ... + 5712788810.

Almost surely, 2^851205521664 is an apocalyptic number.

851205521664 is the 922608-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 851205521664

851205521664 is an abundant number, since it is smaller than the sum of its proper divisors (1764891479469).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

851205521664 is an frugal number, since it uses more digits than its factorization.

851205521664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412 (or 197 counting only the distinct ones).

The product of its (nonzero) digits is 576000, while the sum is 45.

The spelling of 851205521664 in words is "eight hundred fifty-one billion, two hundred five million, five hundred twenty-one thousand, six hundred sixty-four".