78815977 has 2 divisors, whose sum is σ = 78815978. Its totient is φ = 78815976.

The previous prime is 78815951. The next prime is 78815999. The reversal of 78815977 is 77951887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78659161 + 156816 = 8869^2 + 396^2 .

It is a cyclic number.

It is not a de Polignac number, because 78815977 - 2¹⁵ = 78783209 is a prime.

It is not a weakly prime, because it can be changed into another prime (78819977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39407988 + 39407989.

It is an arithmetic number, because the mean of its divisors is an integer number (39407989).

Almost surely, 2^78815977 is an apocalyptic number.

It is an amenable number.

78815977 is a deficient number, since it is larger than the sum of its proper divisors (1).

78815977 is an equidigital number, since it uses as much as digits as its factorization.

78815977 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 987840, while the sum is 52.

The square root of 78815977 is about 8877.8362791842. The cubic root of 78815977 is about 428.7506134907.

The spelling of 78815977 in words is "seventy-eight million, eight hundred fifteen thousand, nine hundred seventy-seven".