21358979 has 2 divisors, whose sum is σ = 21358980. Its totient is φ = 21358978.

The previous prime is 21358951. The next prime is 21358999. The reversal of 21358979 is 97985312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21358979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21358949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10679489 + 10679490.

It is an arithmetic number, because the mean of its divisors is an integer number (10679490).

Almost surely, 2^21358979 is an apocalyptic number.

21358979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21358979 is an equidigital number, since it uses as much as digits as its factorization.

21358979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 136080, while the sum is 44.

The square root of 21358979 is about 4621.5775445188. The cubic root of 21358979 is about 277.4556009372.

The spelling of 21358979 in words is "twenty-one million, three hundred fifty-eight thousand, nine hundred seventy-nine".