81331621900 has 36 divisors (see below), whose sum is σ = 177546480048. Its totient is φ = 32337835840.

The previous prime is 81331621873. The next prime is 81331621907. The reversal of 81331621900 is 912613318.

It is a super-2 number, since 2×81331621900² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81331621907) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2418379 + ... + 2451778.

It is an arithmetic number, because the mean of its divisors is an integer number (4931846668).

Almost surely, 2^81331621900 is an apocalyptic number.

It is an amenable number.

81331621900 is an abundant number, since it is smaller than the sum of its proper divisors (96214858148).

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

81331621900 is a wasteful number, since it uses less digits than its factorization.

81331621900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4870338 (or 4870331 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 34.

The spelling of 81331621900 in words is "eighty-one billion, three hundred thirty-one million, six hundred twenty-one thousand, nine hundred".