21525520 has 20 divisors (see below), whose sum is σ = 50047020. Its totient is φ = 8610176.

The previous prime is 21525481. The next prime is 21525529. The reversal of 21525520 is 2552512.

It can be written as a sum of positive squares in 2 ways, for example, as 14992384 + 6533136 = 3872^2 + 2556^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×21525520² = 926696022540800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21525491 and 21525500.

It is not an unprimeable number, because it can be changed into a prime (21525529) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134455 + ... + 134614.

It is an arithmetic number, because the mean of its divisors is an integer number (2502351).

Almost surely, 2^21525520 is an apocalyptic number.

21525520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21525520 is an abundant number, since it is smaller than the sum of its proper divisors (28521500).

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

21525520 is a wasteful number, since it uses less digits than its factorization.

21525520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269082 (or 269076 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 22.

The square root of 21525520 is about 4639.5603239962. The cubic root of 21525520 is about 278.1748636767.

The spelling of 21525520 in words is "twenty-one million, five hundred twenty-five thousand, five hundred twenty".