21679759 has 4 divisors (see below), whose sum is σ = 21976816. Its totient is φ = 21382704.

The previous prime is 21679753. The next prime is 21679769. The reversal of 21679759 is 95797612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21679759 - 2⁷ = 21679631 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 (21679753) 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, 148419 + ... + 148564.

It is an arithmetic number, because the mean of its divisors is an integer number (5494204).

Almost surely, 2^21679759 is an apocalyptic number.

21679759 is a deficient number, since it is larger than the sum of its proper divisors (297057).

21679759 is an equidigital number, since it uses as much as digits as its factorization.

21679759 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297056.

The product of its digits is 238140, while the sum is 46.

The square root of 21679759 is about 4656.1528110662. The cubic root of 21679759 is about 278.8376945960.

It can be divided in two parts, 2 and 1679759, that added together give a palindrome (1679761).

The spelling of 21679759 in words is "twenty-one million, six hundred seventy-nine thousand, seven hundred fifty-nine".