21320312 has 64 divisors (see below), whose sum is σ = 47174400. Its totient is φ = 8939520.

The previous prime is 21320311. The next prime is 21320317. The reversal of 21320312 is 21302312.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320311) 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 15 ways as a sum of consecutive naturals, for example, 54614 + ... + 55002.

It is an arithmetic number, because the mean of its divisors is an integer number (737100).

Almost surely, 2^21320312 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 21320312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23587200).

21320312 is an abundant number, since it is smaller than the sum of its proper divisors (25854088).

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

21320312 is a wasteful number, since it uses less digits than its factorization.

21320312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 456 (or 452 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21320312 is about 4617.3923376729. The cubic root of 21320312 is about 277.2880702039.

Adding to 21320312 its reverse (21302312), we get a palindrome (42622624).

The spelling of 21320312 in words is "twenty-one million, three hundred twenty thousand, three hundred twelve".