765991 has 2 divisors, whose sum is σ = 765992. Its totient is φ = 765990.

The previous prime is 765983. The next prime is 766021. The reversal of 765991 is 199567.

765991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is an emirp because it is prime and its reverse (199567) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 765991 - 2³ = 765983 is a prime.

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 765991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (765931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 382995 + 382996.

It is an arithmetic number, because the mean of its divisors is an integer number (382996).

2⁷⁶⁵⁹⁹¹ is an apocalyptic number.

765991 is a deficient number, since it is larger than the sum of its proper divisors (1).

765991 is an equidigital number, since it uses as much as digits as its factorization.

765991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17010, while the sum is 37.

The square root of 765991 is about 875.2091178684. The cubic root of 765991 is about 91.4972179074.

It can be divided in two parts, 7659 and 91, that added together give a triangular number (7750 = T₁₂₄).

The spelling of 765991 in words is "seven hundred sixty-five thousand, nine hundred ninety-one".