21664870 has 16 divisors (see below), whose sum is σ = 39051360. Its totient is φ = 8653824.

The previous prime is 21664861. The next prime is 21664879. The reversal of 21664870 is 7846612.

It is an interprime number because it is at equal distance from previous prime (21664861) and next prime (21664879).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10591 + ... + 12469.

It is an arithmetic number, because the mean of its divisors is an integer number (2440710).

Almost surely, 2^21664870 is an apocalyptic number.

21664870 is a deficient number, since it is larger than the sum of its proper divisors (17386490).

21664870 is a wasteful number, since it uses less digits than its factorization.

21664870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3039.

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 21664870 is about 4654.5536842967. The cubic root of 21664870 is about 278.7738475579.

The spelling of 21664870 in words is "twenty-one million, six hundred sixty-four thousand, eight hundred seventy".