21012664 has 16 divisors (see below), whose sum is σ = 40360320. Its totient is φ = 10249920.

The previous prime is 21012661. The next prime is 21012671. The reversal of 21012664 is 46621012.

It is a super-3 number, since 3×21012664³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 31704 + ... + 32359.

It is an arithmetic number, because the mean of its divisors is an integer number (2522520).

Almost surely, 2^21012664 is an apocalyptic number.

It is an amenable number.

21012664 is a deficient number, since it is larger than the sum of its proper divisors (19347656).

21012664 is a wasteful number, since it uses less digits than its factorization.

21012664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64110 (or 64106 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21012664 is about 4583.9572423835. The cubic root of 21012664 is about 275.9478652489.

Adding to 21012664 its reverse (46621012), we get a palindrome (67633676).

The spelling of 21012664 in words is "twenty-one million, twelve thousand, six hundred sixty-four".