21255920 has 40 divisors (see below), whose sum is σ = 56481504. Its totient is φ = 7287552.

The previous prime is 21255919. The next prime is 21255931. The reversal of 21255920 is 2955212.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21255920.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18419 + ... + 19538.

Almost surely, 2^21255920 is an apocalyptic number.

21255920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21255920 is an abundant number, since it is smaller than the sum of its proper divisors (35225584).

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

21255920 is a wasteful number, since it uses less digits than its factorization.

21255920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37977 (or 37971 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 21255920 is about 4610.4142980865. The cubic root of 21255920 is about 277.0086318432.

The spelling of 21255920 in words is "twenty-one million, two hundred fifty-five thousand, nine hundred twenty".