21979929 has 8 divisors (see below), whose sum is σ = 31030560. Its totient is φ = 13791296.

The previous prime is 21979913. The next prime is 21979939. The reversal of 21979929 is 92997912.

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 21979929 - 2⁴ = 21979913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21979939) 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, 215439 + ... + 215540.

It is an arithmetic number, because the mean of its divisors is an integer number (3878820).

Almost surely, 2^21979929 is an apocalyptic number.

It is an amenable number.

21979929 is a deficient number, since it is larger than the sum of its proper divisors (9050631).

21979929 is a wasteful number, since it uses less digits than its factorization.

21979929 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430999.

The product of its digits is 183708, while the sum is 48.

The square root of 21979929 is about 4688.2756958182. The cubic root of 21979929 is about 280.1186954247.

The spelling of 21979929 in words is "twenty-one million, nine hundred seventy-nine thousand, nine hundred twenty-nine".