21621875 has 48 divisors (see below), whose sum is σ = 32060448. Its totient is φ = 14400000.

The previous prime is 21621871. The next prime is 21621881. The reversal of 21621875 is 57812612.

It is not a de Polignac number, because 21621875 - 2² = 21621871 is a prime.

It is a Duffinian number.

Its product of digits (6720) is a multiple of the sum of its prime divisors (70).

It is not an unprimeable number, because it can be changed into a prime (21621871) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 584357 + ... + 584393.

It is an arithmetic number, because the mean of its divisors is an integer number (667926).

Almost surely, 2^21621875 is an apocalyptic number.

21621875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21621875 is a deficient number, since it is larger than the sum of its proper divisors (10438573).

21621875 is an equidigital number, since it uses as much as digits as its factorization.

21621875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90 (or 70 counting only the distinct ones).

The product of its digits is 6720, while the sum is 32.

The square root of 21621875 is about 4649.9327952133. The cubic root of 21621875 is about 278.5893119605.

The spelling of 21621875 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred seventy-five".