21775864 has 32 divisors (see below), whose sum is σ = 44731440. Its totient is φ = 9856000.

The previous prime is 21775837. The next prime is 21775877. The reversal of 21775864 is 46857712.

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, 30714 + ... + 31414.

Almost surely, 2^21775864 is an apocalyptic number.

It is an amenable number.

21775864 is an abundant number, since it is smaller than the sum of its proper divisors (22955576).

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

21775864 is a wasteful number, since it uses less digits than its factorization.

21775864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1071 (or 1067 counting only the distinct ones).

The product of its digits is 94080, while the sum is 40.

The square root of 21775864 is about 4666.4616145427. The cubic root of 21775864 is about 279.2491105528.

The spelling of 21775864 in words is "twenty-one million, seven hundred seventy-five thousand, eight hundred sixty-four".