21660689 has 4 divisors (see below), whose sum is σ = 21704256. Its totient is φ = 21617124.

The previous prime is 21660677. The next prime is 21660701. The reversal of 21660689 is 98606612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21660677) and next prime (21660701).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21660689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21029 + ... + 22034.

It is an arithmetic number, because the mean of its divisors is an integer number (5426064).

Almost surely, 2^21660689 is an apocalyptic number.

It is an amenable number.

21660689 is a deficient number, since it is larger than the sum of its proper divisors (43567).

21660689 is an equidigital number, since it uses as much as digits as its factorization.

21660689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43566.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 21660689 is about 4654.1045325605. The cubic root of 21660689 is about 278.7559133255.

The spelling of 21660689 in words is "twenty-one million, six hundred sixty thousand, six hundred eighty-nine".