21312464 has 20 divisors (see below), whose sum is σ = 41383140. Its totient is φ = 10632960.

The previous prime is 21312463. The next prime is 21312493. The reversal of 21312464 is 46421312.

It can be written as a sum of positive squares in 2 ways, for example, as 8410000 + 12902464 = 2900^2 + 3592^2 .

It is a super-2 number, since 2×21312464² = 908442243502592, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312461) 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, 7934 + ... + 10274.

It is an arithmetic number, because the mean of its divisors is an integer number (2069157).

Almost surely, 2^21312464 is an apocalyptic number.

It is an amenable number.

21312464 is a deficient number, since it is larger than the sum of its proper divisors (20070676).

21312464 is a wasteful number, since it uses less digits than its factorization.

21312464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2918 (or 2912 counting only the distinct ones).

The product of its digits is 1152, while the sum is 23.

The square root of 21312464 is about 4616.5424291346. The cubic root of 21312464 is about 277.2540428119.

Subtracting from 21312464 its product of digits (1152), we obtain a palindrome (21311312).

Adding to 21312464 its reverse (46421312), we get a palindrome (67733776).

The spelling of 21312464 in words is "twenty-one million, three hundred twelve thousand, four hundred sixty-four".