21979565 has 8 divisors (see below), whose sum is σ = 26822880. Its totient is φ = 17285392.

The previous prime is 21979553. The next prime is 21979571. The reversal of 21979565 is 56597912.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21979565 - 2¹⁶ = 21914029 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36959 + ... + 37548.

It is an arithmetic number, because the mean of its divisors is an integer number (3352860).

Almost surely, 2^21979565 is an apocalyptic number.

It is an amenable number.

21979565 is a deficient number, since it is larger than the sum of its proper divisors (4843315).

21979565 is an equidigital number, since it uses as much as digits as its factorization.

21979565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74571.

The product of its digits is 170100, while the sum is 44.

The square root of 21979565 is about 4688.2368754149. The cubic root of 21979565 is about 280.1171491084.

The spelling of 21979565 in words is "twenty-one million, nine hundred seventy-nine thousand, five hundred sixty-five".