21739879 has 12 divisors (see below), whose sum is σ = 26163000. Its totient is φ = 17990448.

The previous prime is 21739877. The next prime is 21739903. The reversal of 21739879 is 97893712.

It is a happy number.

It is not a de Polignac number, because 21739879 - 2¹ = 21739877 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 (21739873) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6229 + ... + 9070.

It is an arithmetic number, because the mean of its divisors is an integer number (2180250).

Almost surely, 2^21739879 is an apocalyptic number.

21739879 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21739879 is a deficient number, since it is larger than the sum of its proper divisors (4423121).

21739879 is a wasteful number, since it uses less digits than its factorization.

21739879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15342 (or 15335 counting only the distinct ones).

The product of its digits is 190512, while the sum is 46.

The square root of 21739879 is about 4662.6043151870. The cubic root of 21739879 is about 279.0952043810.

The spelling of 21739879 in words is "twenty-one million, seven hundred thirty-nine thousand, eight hundred seventy-nine".