391778668387 has 2 divisors, whose sum is σ = 391778668388. Its totient is φ = 391778668386.

The previous prime is 391778668363. The next prime is 391778668433. The reversal of 391778668387 is 783866877193.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 391778668387 - 2²³ = 391770279779 is a prime.

It is not a weakly prime, because it can be changed into another prime (391778668327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195889334193 + 195889334194.

It is an arithmetic number, because the mean of its divisors is an integer number (195889334194).

Almost surely, 2^391778668387 is an apocalyptic number.

391778668387 is a deficient number, since it is larger than the sum of its proper divisors (1).

391778668387 is an equidigital number, since it uses as much as digits as its factorization.

391778668387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 512096256, while the sum is 73.

The spelling of 391778668387 in words is "three hundred ninety-one billion, seven hundred seventy-eight million, six hundred sixty-eight thousand, three hundred eighty-seven".