78391979 has 2 divisors, whose sum is σ = 78391980. Its totient is φ = 78391978.

The previous prime is 78391949. The next prime is 78391987. The reversal of 78391979 is 97919387.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78391979 is a prime.

It is a super-2 number, since 2×78391979² = 12290604743072882, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 78391979.

It is not a weakly prime, because it can be changed into another prime (78391949) 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, 39195989 + 39195990.

It is an arithmetic number, because the mean of its divisors is an integer number (39195990).

Almost surely, 2^78391979 is an apocalyptic number.

78391979 is a deficient number, since it is larger than the sum of its proper divisors (1).

78391979 is an equidigital number, since it uses as much as digits as its factorization.

78391979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 857304, while the sum is 53.

The square root of 78391979 is about 8853.9244970804. The cubic root of 78391979 is about 427.9803958616.

The spelling of 78391979 in words is "seventy-eight million, three hundred ninety-one thousand, nine hundred seventy-nine".