21316864 has 18 divisors (see below), whose sum is σ = 42550970. Its totient is φ = 10658304.

The previous prime is 21316859. The next prime is 21316891. The reversal of 21316864 is 46861312.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 230400 = 4592^2 + 480^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41379 + ... + 41890.

Almost surely, 2^21316864 is an apocalyptic number.

It is an amenable number.

21316864 is a deficient number, since it is larger than the sum of its proper divisors (21234106).

21316864 is an frugal number, since it uses more digits than its factorization.

21316864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83285 (or 83271 counting only the distinct ones).

The product of its digits is 6912, while the sum is 31.

The square root of 21316864 is about 4617.0189516613. The cubic root of 21316864 is about 277.2731213793.

The spelling of 21316864 in words is "twenty-one million, three hundred sixteen thousand, eight hundred sixty-four".