21286520 has 16 divisors (see below), whose sum is σ = 47894760. Its totient is φ = 8514592.

The previous prime is 21286513. The next prime is 21286537. The reversal of 21286520 is 2568212.

It is a self number, because there is not a number n which added to its sum of digits gives 21286520.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266042 + ... + 266121.

Almost surely, 2^21286520 is an apocalyptic number.

21286520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21286520 is an abundant number, since it is smaller than the sum of its proper divisors (26608240).

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

21286520 is a wasteful number, since it uses less digits than its factorization.

21286520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532174 (or 532170 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21286520 is about 4613.7316783706. The cubic root of 21286520 is about 277.1414952182.

The spelling of 21286520 in words is "twenty-one million, two hundred eighty-six thousand, five hundred twenty".