21986665 has 8 divisors (see below), whose sum is σ = 26435520. Its totient is φ = 17554992.

The previous prime is 21986639. The next prime is 21986683. The reversal of 21986665 is 56668912.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21986665 is a prime.

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, 1285 + ... + 6754.

It is an arithmetic number, because the mean of its divisors is an integer number (3304440).

Almost surely, 2^21986665 is an apocalyptic number.

It is an amenable number.

21986665 is a deficient number, since it is larger than the sum of its proper divisors (4448855).

21986665 is an equidigital number, since it uses as much as digits as its factorization.

21986665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8591.

The product of its digits is 155520, while the sum is 43.

The square root of 21986665 is about 4688.9940285737. The cubic root of 21986665 is about 280.1473076921.

The spelling of 21986665 in words is "twenty-one million, nine hundred eighty-six thousand, six hundred sixty-five".