19717979 has 2 divisors, whose sum is σ = 19717980. Its totient is φ = 19717978.

The previous prime is 19717967. The next prime is 19717981. The reversal of 19717979 is 97971791.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19717979 - 2⁸ = 19717723 is a prime.

It is a Sophie Germain prime.

Together with 19717981, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19717879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9858989 + 9858990.

It is an arithmetic number, because the mean of its divisors is an integer number (9858990).

Almost surely, 2^19717979 is an apocalyptic number.

19717979 is a deficient number, since it is larger than the sum of its proper divisors (1).

19717979 is an equidigital number, since it uses as much as digits as its factorization.

19717979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 250047, while the sum is 50.

The square root of 19717979 is about 4440.4931032488. The cubic root of 19717979 is about 270.1598459069.

The spelling of 19717979 in words is "nineteen million, seven hundred seventeen thousand, nine hundred seventy-nine".