81978564 has 24 divisors (see below), whose sum is σ = 192195808. Its totient is φ = 27195840.

The previous prime is 81978551. The next prime is 81978577. The reversal of 81978564 is 46587918.

It is an interprime number because it is at equal distance from previous prime (81978551) and next prime (81978577).

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, 13657 + ... + 18720.

Almost surely, 2^81978564 is an apocalyptic number.

It is an amenable number.

81978564 is an abundant number, since it is smaller than the sum of its proper divisors (110217244).

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

81978564 is a wasteful number, since it uses less digits than its factorization.

81978564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32595 (or 32593 counting only the distinct ones).

The product of its digits is 483840, while the sum is 48.

The square root of 81978564 is about 9054.2014556779. The cubic root of 81978564 is about 434.4102882430.

It can be divided in two parts, 8197 and 8564, that added together give a palindrome (16761).

The spelling of 81978564 in words is "eighty-one million, nine hundred seventy-eight thousand, five hundred sixty-four".