21979719 has 6 divisors (see below), whose sum is σ = 31748496. Its totient is φ = 14653140.

The previous prime is 21979717. The next prime is 21979733. The reversal of 21979719 is 91797912.

It is not a de Polignac number, because 21979719 - 2¹ = 21979717 is a prime.

It is a super-2 number, since 2×21979719² = 966216094637922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21979717) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1221087 + ... + 1221104.

It is an arithmetic number, because the mean of its divisors is an integer number (5291416).

Almost surely, 2^21979719 is an apocalyptic number.

21979719 is a deficient number, since it is larger than the sum of its proper divisors (9768777).

21979719 is a wasteful number, since it uses less digits than its factorization.

21979719 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2442197 (or 2442194 counting only the distinct ones).

The product of its digits is 71442, while the sum is 45.

The square root of 21979719 is about 4688.2532994709. The cubic root of 21979719 is about 280.1178033213.

The spelling of 21979719 in words is "twenty-one million, nine hundred seventy-nine thousand, seven hundred nineteen".