21097520 has 40 divisors (see below), whose sum is σ = 50200656. Its totient is φ = 8241408.

The previous prime is 21097513. The next prime is 21097547. The reversal of 21097520 is 2579012.

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 21097520.

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, 374 + ... + 6506.

Almost surely, 2^21097520 is an apocalyptic number.

21097520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21097520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25100328).

21097520 is an abundant number, since it is smaller than the sum of its proper divisors (29103136).

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

21097520 is a wasteful number, since it uses less digits than its factorization.

21097520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6189 (or 6183 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 26.

The square root of 21097520 is about 4593.2036749964. The cubic root of 21097520 is about 276.3188222160.

The spelling of 21097520 in words is "twenty-one million, ninety-seven thousand, five hundred twenty".