21655760 has 40 divisors (see below), whose sum is σ = 57543936. Its totient is φ = 7424640.

The previous prime is 21655759. The next prime is 21655787. The reversal of 21655760 is 6755612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

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, 18776 + ... + 19895.

Almost surely, 2^21655760 is an apocalyptic number.

21655760 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21655760 is an abundant number, since it is smaller than the sum of its proper divisors (35888176).

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

21655760 is a wasteful number, since it uses less digits than its factorization.

21655760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38691 (or 38685 counting only the distinct ones).

The product of its (nonzero) digits is 12600, while the sum is 32.

The square root of 21655760 is about 4653.5749698484. The cubic root of 21655760 is about 278.7347676126.

The spelling of 21655760 in words is "twenty-one million, six hundred fifty-five thousand, seven hundred sixty".