78815999 has 2 divisors, whose sum is σ = 78816000. Its totient is φ = 78815998.

The previous prime is 78815977. The next prime is 78816007. The reversal of 78815999 is 99951887.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78815999 - 2²⁰ = 77767423 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78812999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39407999 + 39408000.

It is an arithmetic number, because the mean of its divisors is an integer number (39408000).

Almost surely, 2^78815999 is an apocalyptic number.

78815999 is a deficient number, since it is larger than the sum of its proper divisors (1).

78815999 is an equidigital number, since it uses as much as digits as its factorization.

78815999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1632960, while the sum is 56.

The square root of 78815999 is about 8877.8375182248. The cubic root of 78815999 is about 428.7506533832.

The spelling of 78815999 in words is "seventy-eight million, eight hundred fifteen thousand, nine hundred ninety-nine".