78190991 has 2 divisors, whose sum is σ = 78190992. Its totient is φ = 78190990.

The previous prime is 78190967. The next prime is 78190993. The reversal of 78190991 is 19909187.

It is a strong prime.

It is an emirp because it is prime and its reverse (19909187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78190991 - 2¹⁸ = 77928847 is a prime.

It is a super-2 number, since 2×78190991² = 12227662147124162, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 78190993, 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 (78190993) 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, 39095495 + 39095496.

It is an arithmetic number, because the mean of its divisors is an integer number (39095496).

Almost surely, 2^78190991 is an apocalyptic number.

78190991 is a deficient number, since it is larger than the sum of its proper divisors (1).

78190991 is an equidigital number, since it uses as much as digits as its factorization.

78190991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40824, while the sum is 44.

The square root of 78190991 is about 8842.5669915472. The cubic root of 78190991 is about 427.6143186855.

The spelling of 78190991 in words is "seventy-eight million, one hundred ninety thousand, nine hundred ninety-one".