391969939 has 2 divisors, whose sum is σ = 391969940. Its totient is φ = 391969938.

The previous prime is 391969909. The next prime is 391969951. The reversal of 391969939 is 939969193.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 391969939 - 2²⁵ = 358415507 is a prime.

It is not a weakly prime, because it can be changed into another prime (391969909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195984969 + 195984970.

It is an arithmetic number, because the mean of its divisors is an integer number (195984970).

Almost surely, 2^391969939 is an apocalyptic number.

391969939 is a deficient number, since it is larger than the sum of its proper divisors (1).

391969939 is an equidigital number, since it uses as much as digits as its factorization.

391969939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3188646, while the sum is 58.

The square root of 391969939 is about 19798.2307037775. The cubic root of 391969939 is about 731.8424336371.

The spelling of 391969939 in words is "three hundred ninety-one million, nine hundred sixty-nine thousand, nine hundred thirty-nine".