21501872 has 80 divisors (see below), whose sum is σ = 52710912. Its totient is φ = 8279040.

The previous prime is 21501869. The next prime is 21501899. The reversal of 21501872 is 27810512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43547 + ... + 44037.

Almost surely, 2^21501872 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21501872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26355456).

21501872 is an abundant number, since it is smaller than the sum of its proper divisors (31209040).

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

21501872 is a wasteful number, since it uses less digits than its factorization.

21501872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546 (or 540 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21501872 is about 4637.0111063054. The cubic root of 21501872 is about 278.0729584402.

The spelling of 21501872 in words is "twenty-one million, five hundred one thousand, eight hundred seventy-two".