78191831 has 2 divisors, whose sum is σ = 78191832. Its totient is φ = 78191830.

The previous prime is 78191807. The next prime is 78191843. The reversal of 78191831 is 13819187.

It is a strong prime.

It is an emirp because it is prime and its reverse (13819187) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78191831 is a prime.

It is a super-2 number, since 2×78191831² = 12227924870265122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78191131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39095915 + 39095916.

It is an arithmetic number, because the mean of its divisors is an integer number (39095916).

Almost surely, 2^78191831 is an apocalyptic number.

78191831 is a deficient number, since it is larger than the sum of its proper divisors (1).

78191831 is an equidigital number, since it uses as much as digits as its factorization.

78191831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 38.

The square root of 78191831 is about 8842.6144889393. The cubic root of 78191831 is about 427.6158499563.

The spelling of 78191831 in words is "seventy-eight million, one hundred ninety-one thousand, eight hundred thirty-one".