78613991 has 2 divisors, whose sum is σ = 78613992. Its totient is φ = 78613990.

The previous prime is 78613979. The next prime is 78613993. The reversal of 78613991 is 19931687.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78613991 - 2¹⁰ = 78612967 is a prime.

Together with 78613993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78613993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39306995 + 39306996.

It is an arithmetic number, because the mean of its divisors is an integer number (39306996).

Almost surely, 2^78613991 is an apocalyptic number.

78613991 is a deficient number, since it is larger than the sum of its proper divisors (1).

78613991 is an equidigital number, since it uses as much as digits as its factorization.

78613991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 81648, while the sum is 44.

The square root of 78613991 is about 8866.4531239950. The cubic root of 78613991 is about 428.3840393104.

The spelling of 78613991 in words is "seventy-eight million, six hundred thirteen thousand, nine hundred ninety-one".