21123320 has 32 divisors (see below), whose sum is σ = 48636720. Its totient is φ = 8252160.

The previous prime is 21123313. The next prime is 21123331. The reversal of 21123320 is 2332112.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21123295 and 21123304.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4421 + ... + 7860.

Almost surely, 2^21123320 is an apocalyptic number.

21123320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21123320 is an abundant number, since it is smaller than the sum of its proper divisors (27513400).

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

21123320 is a wasteful number, since it uses less digits than its factorization.

21123320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12335 (or 12331 counting only the distinct ones).

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

The square root of 21123320 is about 4596.0113141723. The cubic root of 21123320 is about 276.4314124094.

Adding to 21123320 its reverse (2332112), we get a palindrome (23455432).

The spelling of 21123320 in words is "twenty-one million, one hundred twenty-three thousand, three hundred twenty".