21658664 has 16 divisors (see below), whose sum is σ = 41299200. Its totient is φ = 10645552.

The previous prime is 21658657. The next prime is 21658669. The reversal of 21658664 is 46685612.

It is not an unprimeable number, because it can be changed into a prime (21658669) 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 3 ways as a sum of consecutive naturals, for example, 22472 + ... + 23415.

It is an arithmetic number, because the mean of its divisors is an integer number (2581200).

Almost surely, 2^21658664 is an apocalyptic number.

It is an amenable number.

21658664 is a deficient number, since it is larger than the sum of its proper divisors (19640536).

21658664 is a wasteful number, since it uses less digits than its factorization.

21658664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45952 (or 45948 counting only the distinct ones).

The product of its digits is 69120, while the sum is 38.

The square root of 21658664 is about 4653.8869775705. The cubic root of 21658664 is about 278.7472263393.

It can be divided in two parts, 21658 and 664, that added together give a palindrome (22322).

The spelling of 21658664 in words is "twenty-one million, six hundred fifty-eight thousand, six hundred sixty-four".