21655664 has 10 divisors (see below), whose sum is σ = 41957880. Its totient is φ = 10827824.

The previous prime is 21655657. The next prime is 21655679. The reversal of 21655664 is 46655612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 676724 + ... + 676755.

It is an arithmetic number, because the mean of its divisors is an integer number (4195788).

Almost surely, 2^21655664 is an apocalyptic number.

It is an amenable number.

21655664 is a deficient number, since it is larger than the sum of its proper divisors (20302216).

21655664 is a wasteful number, since it uses less digits than its factorization.

21655664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1353487 (or 1353481 counting only the distinct ones).

The product of its digits is 43200, while the sum is 35.

The square root of 21655664 is about 4653.5646551864. The cubic root of 21655664 is about 278.7343557349.

The spelling of 21655664 in words is "twenty-one million, six hundred fifty-five thousand, six hundred sixty-four".