391540979 has 2 divisors, whose sum is σ = 391540980. Its totient is φ = 391540978.

The previous prime is 391540969. The next prime is 391540997. The reversal of 391540979 is 979045193.

Together with next prime (391540997) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 391540979 - 2²⁸ = 123105523 is a prime.

It is not a weakly prime, because it can be changed into another prime (391540949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195770489 + 195770490.

It is an arithmetic number, because the mean of its divisors is an integer number (195770490).

Almost surely, 2^391540979 is an apocalyptic number.

391540979 is a deficient number, since it is larger than the sum of its proper divisors (1).

391540979 is an equidigital number, since it uses as much as digits as its factorization.

391540979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 306180, while the sum is 47.

The square root of 391540979 is about 19787.3944469705. The cubic root of 391540979 is about 731.5753674774.

The spelling of 391540979 in words is "three hundred ninety-one million, five hundred forty thousand, nine hundred seventy-nine".