21031312 has 40 divisors (see below), whose sum is σ = 43497216. Its totient is φ = 9816576.

The previous prime is 21031303. The next prime is 21031313. The reversal of 21031312 is 21313012.

It is a junction number, because it is equal to n+sod(n) for n = 21031292 and 21031301.

It is not an unprimeable number, because it can be changed into a prime (21031313) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45193 + ... + 45655.

Almost surely, 2^21031312 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21031312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21748608).

21031312 is an abundant number, since it is smaller than the sum of its proper divisors (22465904).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21031312 is a wasteful number, since it uses less digits than its factorization.

21031312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 655 (or 649 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21031312 is about 4585.9908416830. The cubic root of 21031312 is about 276.0294724531.

Adding to 21031312 its reverse (21313012), we get a palindrome (42344324).

The spelling of 21031312 in words is "twenty-one million, thirty-one thousand, three hundred twelve".