78191591 has 2 divisors, whose sum is σ = 78191592. Its totient is φ = 78191590.

The previous prime is 78191557. The next prime is 78191599. The reversal of 78191591 is 19519187.

It is a strong prime.

It is an emirp because it is prime and its reverse (19519187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78191591 - 2⁶ = 78191527 is a prime.

It is a super-2 number, since 2×78191591² = 12227849806222562, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78191599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39095795 + 39095796.

It is an arithmetic number, because the mean of its divisors is an integer number (39095796).

Almost surely, 2^78191591 is an apocalyptic number.

78191591 is a deficient number, since it is larger than the sum of its proper divisors (1).

78191591 is an equidigital number, since it uses as much as digits as its factorization.

78191591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 41.

The square root of 78191591 is about 8842.6009182819. The cubic root of 78191591 is about 427.6154124515.

The spelling of 78191591 in words is "seventy-eight million, one hundred ninety-one thousand, five hundred ninety-one".