21659679 has 6 divisors (see below), whose sum is σ = 31286216. Its totient is φ = 14439780.

The previous prime is 21659657. The next prime is 21659699. The reversal of 21659679 is 97695612.

It is a happy number.

It is not a de Polignac number, because 21659679 - 2⁹ = 21659167 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21659609) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1203307 + ... + 1203324.

Almost surely, 2^21659679 is an apocalyptic number.

21659679 is a deficient number, since it is larger than the sum of its proper divisors (9626537).

21659679 is a wasteful number, since it uses less digits than its factorization.

21659679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2406637 (or 2406634 counting only the distinct ones).

The product of its digits is 204120, while the sum is 45.

The square root of 21659679 is about 4653.9960249231. The cubic root of 21659679 is about 278.7515806247.

It can be divided in two parts, 216 and 59679, that added together give a palindrome (59895).

The spelling of 21659679 in words is "twenty-one million, six hundred fifty-nine thousand, six hundred seventy-nine".