21572538 has 32 divisors (see below), whose sum is σ = 46702656. Its totient is φ = 6603648.

The previous prime is 21572533. The next prime is 21572539. The reversal of 21572538 is 83527512.

It is a super-2 number, since 2×21572538² = 930748791522888, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21572499 and 21572508.

It is not an unprimeable number, because it can be changed into a prime (21572531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17581 + ... + 18767.

It is an arithmetic number, because the mean of its divisors is an integer number (1459458).

Almost surely, 2^21572538 is an apocalyptic number.

21572538 is an abundant number, since it is smaller than the sum of its proper divisors (25130118).

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

21572538 is a wasteful number, since it uses less digits than its factorization.

21572538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1438.

The product of its digits is 16800, while the sum is 33.

The square root of 21572538 is about 4644.6246349947. The cubic root of 21572538 is about 278.3772546733.

The spelling of 21572538 in words is "twenty-one million, five hundred seventy-two thousand, five hundred thirty-eight".