81921860 has 24 divisors (see below), whose sum is σ = 179516736. Its totient is φ = 31343840.

The previous prime is 81921857. The next prime is 81921881. The reversal of 81921860 is 6812918.

It is a super-2 number, since 2×81921860² = 13422382291719200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81921860.

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, 88586 + ... + 89505.

It is an arithmetic number, because the mean of its divisors is an integer number (7479864).

Almost surely, 2^81921860 is an apocalyptic number.

It is an amenable number.

81921860 is an abundant number, since it is smaller than the sum of its proper divisors (97594876).

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

81921860 is a wasteful number, since it uses less digits than its factorization.

81921860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178123 (or 178121 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 81921860 is about 9051.0695500587. The cubic root of 81921860 is about 434.3101056204.

The spelling of 81921860 in words is "eighty-one million, nine hundred twenty-one thousand, eight hundred sixty".