21156520 has 64 divisors (see below), whose sum is σ = 59356800. Its totient is φ = 6593280.

The previous prime is 21156511. The next prime is 21156521. The reversal of 21156520 is 2565112.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a junction number, because it is equal to n+sod(n) for n = 21156491 and 21156500.

It is not an unprimeable number, because it can be changed into a prime (21156521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 355 + ... + 6514.

It is an arithmetic number, because the mean of its divisors is an integer number (927450).

Almost surely, 2^21156520 is an apocalyptic number.

21156520 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 21156520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29678400).

21156520 is an abundant number, since it is smaller than the sum of its proper divisors (38200280).

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

21156520 is a wasteful number, since it uses less digits than its factorization.

21156520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6898 (or 6894 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 22.

The square root of 21156520 is about 4599.6217235768. The cubic root of 21156520 is about 276.5761611029.

The spelling of 21156520 in words is "twenty-one million, one hundred fifty-six thousand, five hundred twenty".