21664250 has 32 divisors (see below), whose sum is σ = 40856400. Its totient is φ = 8601600.

The previous prime is 21664207. The next prime is 21664267. The reversal of 21664250 is 5246612.

It can be written as a sum of positive squares in 8 ways, for example, as 218089 + 21446161 = 467^2 + 4631^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48026 + ... + 48474.

Almost surely, 2^21664250 is an apocalyptic number.

21664250 is a deficient number, since it is larger than the sum of its proper divisors (19192150).

21664250 is a wasteful number, since it uses less digits than its factorization.

21664250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 659 (or 649 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21664250 is about 4654.4870823755. The cubic root of 21664250 is about 278.7711882384.

The spelling of 21664250 in words is "twenty-one million, six hundred sixty-four thousand, two hundred fifty".