21621975 has 12 divisors (see below), whose sum is σ = 35748456. Its totient is φ = 11531680.

The previous prime is 21621967. The next prime is 21621997. The reversal of 21621975 is 57912612.

It is not a de Polignac number, because 21621975 - 2³ = 21621967 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 144072 + ... + 144221.

It is an arithmetic number, because the mean of its divisors is an integer number (2979038).

Almost surely, 2^21621975 is an apocalyptic number.

21621975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21621975 is a deficient number, since it is larger than the sum of its proper divisors (14126481).

21621975 is a wasteful number, since it uses less digits than its factorization.

21621975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 288306 (or 288301 counting only the distinct ones).

The product of its digits is 7560, while the sum is 33.

The square root of 21621975 is about 4649.9435480444. The cubic root of 21621975 is about 278.5897414466.

The spelling of 21621975 in words is "twenty-one million, six hundred twenty-one thousand, nine hundred seventy-five".