21086520 has 128 divisors (see below), whose sum is σ = 77898240. Its totient is φ = 4446720.

The previous prime is 21086501. The next prime is 21086543. The reversal of 21086520 is 2568012.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9955 + ... + 11885.

It is an arithmetic number, because the mean of its divisors is an integer number (608580).

Almost surely, 2^21086520 is an apocalyptic number.

21086520 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 21086520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38949120).

21086520 is an abundant number, since it is smaller than the sum of its proper divisors (56811720).

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

21086520 is a wasteful number, since it uses less digits than its factorization.

21086520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1965 (or 1961 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 21086520 is about 4592.0060975569. The cubic root of 21086520 is about 276.2707907341.

The spelling of 21086520 in words is "twenty-one million, eighty-six thousand, five hundred twenty".