21312436 has 12 divisors (see below), whose sum is σ = 37535428. Its totient is φ = 10588032.

The previous prime is 21312427. The next prime is 21312437. The reversal of 21312436 is 63421312.

It can be written as a sum of positive squares in 2 ways, for example, as 15523600 + 5788836 = 3940^2 + 2406^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312437) 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, 16341 + ... + 17596.

Almost surely, 2^21312436 is an apocalyptic number.

It is an amenable number.

21312436 is a deficient number, since it is larger than the sum of its proper divisors (16222992).

21312436 is a wasteful number, since it uses less digits than its factorization.

21312436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34098 (or 34096 counting only the distinct ones).

The product of its digits is 864, while the sum is 22.

The square root of 21312436 is about 4616.5393965610. The cubic root of 21312436 is about 277.2539213944.

Adding to 21312436 its reverse (63421312), we get a palindrome (84733748).

The spelling of 21312436 in words is "twenty-one million, three hundred twelve thousand, four hundred thirty-six".