21121320 has 64 divisors (see below), whose sum is σ = 69128640. Its totient is φ = 5120000.

The previous prime is 21121319. The next prime is 21121333. The reversal of 21121320 is 2312112.

It is a super-2 number, since 2×21121320² = 892220317084800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21121296 and 21121305.

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, 6681 + ... + 9320.

It is an arithmetic number, because the mean of its divisors is an integer number (1080135).

Almost surely, 2^21121320 is an apocalyptic number.

21121320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121320 is an abundant number, since it is smaller than the sum of its proper divisors (48007320).

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

21121320 is a wasteful number, since it uses less digits than its factorization.

21121320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16026 (or 16022 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21121320 is about 4595.7937290527. The cubic root of 21121320 is about 276.4226877665.

Adding to 21121320 its reverse (2312112), we get a palindrome (23433432).

The spelling of 21121320 in words is "twenty-one million, one hundred twenty-one thousand, three hundred twenty".