78905591 has 2 divisors, whose sum is σ = 78905592. Its totient is φ = 78905590.

The previous prime is 78905581. The next prime is 78905599. The reversal of 78905591 is 19550987.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78905591 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78905599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39452795 + 39452796.

It is an arithmetic number, because the mean of its divisors is an integer number (39452796).

Almost surely, 2^78905591 is an apocalyptic number.

78905591 is a deficient number, since it is larger than the sum of its proper divisors (1).

78905591 is an equidigital number, since it uses as much as digits as its factorization.

78905591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 113400, while the sum is 44.

The square root of 78905591 is about 8882.8819084799. The cubic root of 78905591 is about 428.9130488501.

The spelling of 78905591 in words is "seventy-eight million, nine hundred five thousand, five hundred ninety-one".