21864975 has 48 divisors (see below), whose sum is σ = 41783040. Its totient is φ = 9971200.

The previous prime is 21864959. The next prime is 21864989. The reversal of 21864975 is 57946812.

It is a Cunningham number, because it is equal to 4676²-1.

It is not a de Polignac number, because 21864975 - 2⁴ = 21864959 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 13246 + ... + 14804.

It is an arithmetic number, because the mean of its divisors is an integer number (870480).

Almost surely, 2^21864975 is an apocalyptic number.

21864975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21864975 is a deficient number, since it is larger than the sum of its proper divisors (19918065).

21864975 is a wasteful number, since it uses less digits than its factorization.

21864975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1600 (or 1595 counting only the distinct ones).

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

The square root of 21864975 is about 4675.9998930710. Note that the first 3 decimals coincide. The cubic root of 21864975 is about 279.6295057288.

The spelling of 21864975 in words is "twenty-one million, eight hundred sixty-four thousand, nine hundred seventy-five".