78991439 has 2 divisors, whose sum is σ = 78991440. Its totient is φ = 78991438.

The previous prime is 78991399. The next prime is 78991463. The reversal of 78991439 is 93419987.

It is a strong prime.

It is an emirp because it is prime and its reverse (93419987) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78991439 is a prime.

It is a Sophie Germain 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 (78991139) 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, 39495719 + 39495720.

It is an arithmetic number, because the mean of its divisors is an integer number (39495720).

Almost surely, 2^78991439 is an apocalyptic number.

78991439 is a deficient number, since it is larger than the sum of its proper divisors (1).

78991439 is an equidigital number, since it uses as much as digits as its factorization.

78991439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 489888, while the sum is 50.

The square root of 78991439 is about 8887.7128103917. The cubic root of 78991439 is about 429.0685426132.

The spelling of 78991439 in words is "seventy-eight million, nine hundred ninety-one thousand, four hundred thirty-nine".