21120520 has 16 divisors (see below), whose sum is σ = 47521260. Its totient is φ = 8448192.

The previous prime is 21120503. The next prime is 21120523. The reversal of 21120520 is 2502112.

It can be written as a sum of positive squares in 2 ways, for example, as 20593444 + 527076 = 4538^2 + 726^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21120520.

It is not an unprimeable number, because it can be changed into a prime (21120523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 263967 + ... + 264046.

Almost surely, 2^21120520 is an apocalyptic number.

21120520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21120520 is an abundant number, since it is smaller than the sum of its proper divisors (26400740).

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

21120520 is a wasteful number, since it uses less digits than its factorization.

21120520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 528024 (or 528020 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21120520 is about 4595.7066921204. The cubic root of 21120520 is about 276.4191977551.

Adding to 21120520 its reverse (2502112), we get a palindrome (23622632).

The spelling of 21120520 in words is "twenty-one million, one hundred twenty thousand, five hundred twenty".