21979731 has 8 divisors (see below), whose sum is σ = 30021264. Its totient is φ = 14295680.

The previous prime is 21979717. The next prime is 21979733. The reversal of 21979731 is 13797912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21979731 - 2⁷ = 21979603 is a prime.

It is a super-2 number, since 2×21979731² = 966217149664722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21979731.

It is not an unprimeable number, because it can be changed into a prime (21979733) 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 7 ways as a sum of consecutive naturals, for example, 89226 + ... + 89471.

It is an arithmetic number, because the mean of its divisors is an integer number (3752658).

Almost surely, 2^21979731 is an apocalyptic number.

21979731 is a deficient number, since it is larger than the sum of its proper divisors (8041533).

21979731 is a wasteful number, since it uses less digits than its factorization.

21979731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178741.

The product of its digits is 23814, while the sum is 39.

The square root of 21979731 is about 4688.2545792651. The cubic root of 21979731 is about 280.1178542988.

The spelling of 21979731 in words is "twenty-one million, nine hundred seventy-nine thousand, seven hundred thirty-one".