21105664 has 22 divisors (see below), whose sum is σ = 42192764. Its totient is φ = 10552320.

The previous prime is 21105661. The next prime is 21105671. The reversal of 21105664 is 46650112.

It is not an unprimeable number, because it can be changed into a prime (21105661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9282 + ... + 11329.

Almost surely, 2^21105664 is an apocalyptic number.

It is an amenable number.

21105664 is a deficient number, since it is larger than the sum of its proper divisors (21087100).

21105664 is an equidigital number, since it uses as much as digits as its factorization.

21105664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20631 (or 20613 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21105664 is about 4594.0901166608. The cubic root of 21105664 is about 276.3543722237.

Adding to 21105664 its reverse (46650112), we get a palindrome (67755776).

The spelling of 21105664 in words is "twenty-one million, one hundred five thousand, six hundred sixty-four".