21679689 has 4 divisors (see below), whose sum is σ = 28906256. Its totient is φ = 14453124.

The previous prime is 21679687. The next prime is 21679711. The reversal of 21679689 is 98697612.

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 not a de Polignac number, because 21679689 - 2¹ = 21679687 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21679681) 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, 3613279 + ... + 3613284.

It is an arithmetic number, because the mean of its divisors is an integer number (7226564).

Almost surely, 2^21679689 is an apocalyptic number.

It is an amenable number.

21679689 is a deficient number, since it is larger than the sum of its proper divisors (7226567).

21679689 is an equidigital number, since it uses as much as digits as its factorization.

21679689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7226566.

The product of its digits is 326592, while the sum is 48.

The square root of 21679689 is about 4656.1452941247. The cubic root of 21679689 is about 278.8373944903.

The spelling of 21679689 in words is "twenty-one million, six hundred seventy-nine thousand, six hundred eighty-nine".