21540720 has 40 divisors (see below), whose sum is σ = 66776976. Its totient is φ = 5744128.

The previous prime is 21540709. The next prime is 21540731. The reversal of 21540720 is 2704512.

It is an interprime number because it is at equal distance from previous prime (21540709) and next prime (21540731).

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, 44637 + ... + 45116.

Almost surely, 2^21540720 is an apocalyptic number.

21540720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21540720 is an abundant number, since it is smaller than the sum of its proper divisors (45236256).

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

21540720 is a wasteful number, since it uses less digits than its factorization.

21540720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89769 (or 89763 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 21540720 is about 4641.1981211752. The cubic root of 21540720 is about 278.2403249381.

The spelling of 21540720 in words is "twenty-one million, five hundred forty thousand, seven hundred twenty".