78911993 has 2 divisors, whose sum is σ = 78911994. Its totient is φ = 78911992.

The previous prime is 78911981. The next prime is 78911999. The reversal of 78911993 is 39911987.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50737129 + 28174864 = 7123^2 + 5308^2 .

It is a cyclic number.

It is not a de Polignac number, because 78911993 - 2⁸ = 78911737 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (78911999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39455996 + 39455997.

It is an arithmetic number, because the mean of its divisors is an integer number (39455997).

Almost surely, 2^78911993 is an apocalyptic number.

It is an amenable number.

78911993 is a deficient number, since it is larger than the sum of its proper divisors (1).

78911993 is an equidigital number, since it uses as much as digits as its factorization.

78911993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 122472, while the sum is 47.

The square root of 78911993 is about 8883.2422571942. The cubic root of 78911993 is about 428.9246484806.

The spelling of 78911993 in words is "seventy-eight million, nine hundred eleven thousand, nine hundred ninety-three".