21510972 has 36 divisors (see below), whose sum is σ = 62143536. Its totient is φ = 6145920.

The previous prime is 21510961. The next prime is 21510977. The reversal of 21510972 is 27901512.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21510977) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42429 + ... + 42932.

Almost surely, 2^21510972 is an apocalyptic number.

It is an amenable number.

21510972 is an abundant number, since it is smaller than the sum of its proper divisors (40632564).

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

21510972 is a wasteful number, since it uses less digits than its factorization.

21510972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85378 (or 85373 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21510972 is about 4637.9922380271. The cubic root of 21510972 is about 278.1121814906.

The spelling of 21510972 in words is "twenty-one million, five hundred ten thousand, nine hundred seventy-two".