78987691 has 2 divisors, whose sum is σ = 78987692. Its totient is φ = 78987690.

The previous prime is 78987673. The next prime is 78987703. The reversal of 78987691 is 19678987.

It is a strong prime.

It is an emirp because it is prime and its reverse (19678987) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78987691 is a prime.

It is a super-2 number, since 2×78987691² = 12478110659022962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78987611) 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, 39493845 + 39493846.

It is an arithmetic number, because the mean of its divisors is an integer number (39493846).

Almost surely, 2^78987691 is an apocalyptic number.

78987691 is a deficient number, since it is larger than the sum of its proper divisors (1).

78987691 is an equidigital number, since it uses as much as digits as its factorization.

78987691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1524096, while the sum is 55.

The square root of 78987691 is about 8887.5019549928. The cubic root of 78987691 is about 429.0617563321.

The spelling of 78987691 in words is "seventy-eight million, nine hundred eighty-seven thousand, six hundred ninety-one".