21290979 has 4 divisors (see below), whose sum is σ = 28387976. Its totient is φ = 14193984.

The previous prime is 21290933. The next prime is 21290999. The reversal of 21290979 is 97909212.

It is a happy number.

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

It is not a de Polignac number, because 21290979 - 2¹¹ = 21288931 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21290999) 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, 3548494 + ... + 3548499.

It is an arithmetic number, because the mean of its divisors is an integer number (7096994).

Almost surely, 2^21290979 is an apocalyptic number.

21290979 is a deficient number, since it is larger than the sum of its proper divisors (7096997).

21290979 is an equidigital number, since it uses as much as digits as its factorization.

21290979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7096996.

The product of its (nonzero) digits is 20412, while the sum is 39.

The square root of 21290979 is about 4614.2148844630. The cubic root of 21290979 is about 277.1608452991.

The spelling of 21290979 in words is "twenty-one million, two hundred ninety thousand, nine hundred seventy-nine".