21231320 has 64 divisors (see below), whose sum is σ = 52907040. Its totient is φ = 7603200.

The previous prime is 21231313. The next prime is 21231359. The reversal of 21231320 is 2313212.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21231295 and 21231304.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31790 + ... + 32450.

Almost surely, 2^21231320 is an apocalyptic number.

21231320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21231320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26453520).

21231320 is an abundant number, since it is smaller than the sum of its proper divisors (31675720).

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

21231320 is a wasteful number, since it uses less digits than its factorization.

21231320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 756 (or 752 counting only the distinct ones).

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

The square root of 21231320 is about 4607.7456527026. The cubic root of 21231320 is about 276.9017276197.

Adding to 21231320 its reverse (2313212), we get a palindrome (23544532).

It can be divided in two parts, 2123 and 1320, that added together give a palindrome (3443).

The spelling of 21231320 in words is "twenty-one million, two hundred thirty-one thousand, three hundred twenty".