21684975 has 48 divisors (see below), whose sum is σ = 40330752. Its totient is φ = 10200960.

The previous prime is 21684967. The next prime is 21684977. The reversal of 21684975 is 57948612.

It is not a de Polignac number, because 21684975 - 2³ = 21684967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684977) 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, 21942 + ... + 22908.

It is an arithmetic number, because the mean of its divisors is an integer number (840224).

Almost surely, 2^21684975 is an apocalyptic number.

21684975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21684975 is a deficient number, since it is larger than the sum of its proper divisors (18645777).

21684975 is a wasteful number, since it uses less digits than its factorization.

21684975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1016 (or 1011 counting only the distinct ones).

The product of its digits is 120960, while the sum is 42.

The square root of 21684975 is about 4656.7128964539. The cubic root of 21684975 is about 278.8600549428.

The spelling of 21684975 in words is "twenty-one million, six hundred eighty-four thousand, nine hundred seventy-five".