21660691 has 8 divisors (see below), whose sum is σ = 23870000. Its totient is φ = 19528992.

The previous prime is 21660677. The next prime is 21660701. The reversal of 21660691 is 19606612.

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 21660691 - 2¹¹ = 21658643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660491) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18816 + ... + 19933.

It is an arithmetic number, because the mean of its divisors is an integer number (2983750).

Almost surely, 2^21660691 is an apocalyptic number.

21660691 is a deficient number, since it is larger than the sum of its proper divisors (2209309).

21660691 is a wasteful number, since it uses less digits than its factorization.

21660691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38805.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 21660691 is about 4654.1047474246. The cubic root of 21660691 is about 278.7559219049.

The spelling of 21660691 in words is "twenty-one million, six hundred sixty thousand, six hundred ninety-one".