21520765 has 16 divisors (see below), whose sum is σ = 29922048. Its totient is φ = 14553216.

The previous prime is 21520747. The next prime is 21520771. The reversal of 21520765 is 56702512.

It is a cyclic number.

It is not a de Polignac number, because 21520765 - 2⁷ = 21520637 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 1657 + ... + 6766.

It is an arithmetic number, because the mean of its divisors is an integer number (1870128).

Almost surely, 2^21520765 is an apocalyptic number.

It is an amenable number.

21520765 is a deficient number, since it is larger than the sum of its proper divisors (8401283).

21520765 is an equidigital number, since it uses as much as digits as its factorization.

21520765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8508.

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 21520765 is about 4639.0478548944. The cubic root of 21520765 is about 278.1543791714.

The spelling of 21520765 in words is "twenty-one million, five hundred twenty thousand, seven hundred sixty-five".