21619979 has 2 divisors, whose sum is σ = 21619980. Its totient is φ = 21619978.

The previous prime is 21619973. The next prime is 21619991. The reversal of 21619979 is 97991612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21619979 - 2⁴ = 21619963 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21619973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10809989 + 10809990.

It is an arithmetic number, because the mean of its divisors is an integer number (10809990).

Almost surely, 2^21619979 is an apocalyptic number.

21619979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21619979 is an equidigital number, since it uses as much as digits as its factorization.

21619979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 61236, while the sum is 44.

The square root of 21619979 is about 4649.7289168295. The cubic root of 21619979 is about 278.5811686523.

The spelling of 21619979 in words is "twenty-one million, six hundred nineteen thousand, nine hundred seventy-nine".