21231312 has 20 divisors (see below), whose sum is σ = 54847680. Its totient is φ = 7077088.

The previous prime is 21231307. The next prime is 21231313. The reversal of 21231312 is 21313212.

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21231291 and 21231300.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231313) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 221112 + ... + 221207.

It is an arithmetic number, because the mean of its divisors is an integer number (2742384).

Almost surely, 2^21231312 is an apocalyptic number.

It is an amenable number.

21231312 is an abundant number, since it is smaller than the sum of its proper divisors (33616368).

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

21231312 is a wasteful number, since it uses less digits than its factorization.

21231312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442330 (or 442324 counting only the distinct ones).

The product of its digits is 72, while the sum is 15.

The square root of 21231312 is about 4607.7447845991. The cubic root of 21231312 is about 276.9016928407.

Adding to 21231312 its reverse (21313212), we get a palindrome (42544524).

The spelling of 21231312 in words is "twenty-one million, two hundred thirty-one thousand, three hundred twelve".