21079979 has 2 divisors, whose sum is σ = 21079980. Its totient is φ = 21079978.

The previous prime is 21079931. The next prime is 21079997. The reversal of 21079979 is 97997012.

Together with next prime (21079997) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21079979 - 2²⁴ = 4302763 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21079999) 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 as a sum of consecutive naturals, namely, 10539989 + 10539990.

It is an arithmetic number, because the mean of its divisors is an integer number (10539990).

Almost surely, 2^21079979 is an apocalyptic number.

21079979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21079979 is an equidigital number, since it uses as much as digits as its factorization.

21079979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 71442, while the sum is 44.

The square root of 21079979 is about 4591.2938263631. The cubic root of 21079979 is about 276.2422215482.

The spelling of 21079979 in words is "twenty-one million, seventy-nine thousand, nine hundred seventy-nine".