678139691 has 2 divisors, whose sum is σ = 678139692. Its totient is φ = 678139690.

The previous prime is 678139667. The next prime is 678139699. The reversal of 678139691 is 196931876.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 678139691 - 2²² = 673945387 is a prime.

It is not a weakly prime, because it can be changed into another prime (678139699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 339069845 + 339069846.

It is an arithmetic number, because the mean of its divisors is an integer number (339069846).

Almost surely, 2^678139691 is an apocalyptic number.

678139691 is a deficient number, since it is larger than the sum of its proper divisors (1).

678139691 is an equidigital number, since it uses as much as digits as its factorization.

678139691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 489888, while the sum is 50.

The square root of 678139691 is about 26041.1153946984. The cubic root of 678139691 is about 878.5632940246.

The spelling of 678139691 in words is "six hundred seventy-eight million, one hundred thirty-nine thousand, six hundred ninety-one".