978688391 has 2 divisors, whose sum is σ = 978688392. Its totient is φ = 978688390.

The previous prime is 978688357. The next prime is 978688397. The reversal of 978688391 is 193886879.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-978688391 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 978688391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (978688397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 489344195 + 489344196.

It is an arithmetic number, because the mean of its divisors is an integer number (489344196).

Almost surely, 2^978688391 is an apocalyptic number.

978688391 is a deficient number, since it is larger than the sum of its proper divisors (1).

978688391 is an equidigital number, since it uses as much as digits as its factorization.

978688391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5225472, while the sum is 59.

The square root of 978688391 is about 31283.9957646078. The cubic root of 978688391 is about 992.8450592509.

The spelling of 978688391 in words is "nine hundred seventy-eight million, six hundred eighty-eight thousand, three hundred ninety-one".