21970565 has 4 divisors (see below), whose sum is σ = 26364684. Its totient is φ = 17576448.

The previous prime is 21970513. The next prime is 21970577. The reversal of 21970565 is 56507912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13315201 + 8655364 = 3649^2 + 2942^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21970565 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 3 ways as a sum of consecutive naturals, for example, 2197052 + ... + 2197061.

It is an arithmetic number, because the mean of its divisors is an integer number (6591171).

Almost surely, 2^21970565 is an apocalyptic number.

It is an amenable number.

21970565 is a deficient number, since it is larger than the sum of its proper divisors (4394119).

21970565 is an equidigital number, since it uses as much as digits as its factorization.

21970565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4394118.

The product of its (nonzero) digits is 18900, while the sum is 35.

The square root of 21970565 is about 4687.2769280255. The cubic root of 21970565 is about 280.0789105822.

The spelling of 21970565 in words is "twenty-one million, nine hundred seventy thousand, five hundred sixty-five".