21666985 has 8 divisors (see below), whose sum is σ = 26839296. Its totient is φ = 16774320.

The previous prime is 21666979. The next prime is 21666991. The reversal of 21666985 is 58966612.

It is an interprime number because it is at equal distance from previous prime (21666979) and next prime (21666991).

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

It is a de Polignac number, because none of the positive numbers 2^k-21666985 is a prime.

It is a Duffinian 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, 69739 + ... + 70048.

It is an arithmetic number, because the mean of its divisors is an integer number (3354912).

Almost surely, 2^21666985 is an apocalyptic number.

It is an amenable number.

21666985 is a deficient number, since it is larger than the sum of its proper divisors (5172311).

21666985 is a wasteful number, since it uses less digits than its factorization.

21666985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139823.

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

The square root of 21666985 is about 4654.7808756160. The cubic root of 21666985 is about 278.7829188871.

The spelling of 21666985 in words is "twenty-one million, six hundred sixty-six thousand, nine hundred eighty-five".