81562640256 has 320 divisors, whose sum is σ = 257923116000. Its totient is φ = 25497206784.

The previous prime is 81562640219. The next prime is 81562640267. The reversal of 81562640256 is 65204626518.

81562640256 is a `hidden beast` number, since 8 + 1 + 562 + 64 + 0 + 25 + 6 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 63275260 + ... + 63276548.

Almost surely, 2^81562640256 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81562640256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128961558000).

81562640256 is an abundant number, since it is smaller than the sum of its proper divisors (176360475744).

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

81562640256 is a wasteful number, since it uses less digits than its factorization.

81562640256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1691 (or 1670 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 45.

The spelling of 81562640256 in words is "eighty-one billion, five hundred sixty-two million, six hundred forty thousand, two hundred fifty-six".