81921875 has 42 divisors (see below), whose sum is σ = 120232836. Its totient is φ = 55650000.

The previous prime is 81921857. The next prime is 81921881. The reversal of 81921875 is 57812918.

It is not a de Polignac number, because 81921875 - 2¹⁶ = 81856339 is a prime.

It is a super-2 number, since 2×81921875² = 13422387207031250, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 41 ways as a sum of consecutive naturals, for example, 765572 + ... + 765678.

Almost surely, 2^81921875 is an apocalyptic number.

81921875 is a deficient number, since it is larger than the sum of its proper divisors (38310961).

81921875 is an frugal number, since it uses more digits than its factorization.

81921875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 119 counting only the distinct ones).

The product of its digits is 40320, while the sum is 41.

The square root of 81921875 is about 9051.0703786900. The cubic root of 81921875 is about 434.3101321280.

The spelling of 81921875 in words is "eighty-one million, nine hundred twenty-one thousand, eight hundred seventy-five".