19819979 has 2 divisors, whose sum is σ = 19819980. Its totient is φ = 19819978.

The previous prime is 19819903. The next prime is 19819991. The reversal of 19819979 is 97991891.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19819979 - 2¹⁶ = 19754443 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19819979.

It is not a weakly prime, because it can be changed into another prime (19819999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9909989 + 9909990.

It is an arithmetic number, because the mean of its divisors is an integer number (9909990).

Almost surely, 2^19819979 is an apocalyptic number.

19819979 is a deficient number, since it is larger than the sum of its proper divisors (1).

19819979 is an equidigital number, since it uses as much as digits as its factorization.

19819979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 367416, while the sum is 53.

The square root of 19819979 is about 4451.9634994011. The cubic root of 19819979 is about 270.6248855310.

The spelling of 19819979 in words is "nineteen million, eight hundred nineteen thousand, nine hundred seventy-nine".