81520901812 has 24 divisors (see below), whose sum is σ = 164214774080. Its totient is φ = 34686178560.

The previous prime is 81520901807. The next prime is 81520901843. The reversal of 81520901812 is 21810902518.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10468989 + ... + 10476772.

Almost surely, 2^81520901812 is an apocalyptic number.

It is an amenable number.

81520901812 is an abundant number, since it is smaller than the sum of its proper divisors (82693872268).

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

81520901812 is a wasteful number, since it uses less digits than its factorization.

81520901812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20945911 (or 20945909 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 37.

The spelling of 81520901812 in words is "eighty-one billion, five hundred twenty million, nine hundred one thousand, eight hundred twelve".