780991 has 2 divisors, whose sum is σ = 780992. Its totient is φ = 780990.

The previous prime is 780973. The next prime is 781003. The reversal of 780991 is 199087.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-780991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (780931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390495 + 390496.

It is an arithmetic number, because the mean of its divisors is an integer number (390496).

2⁷⁸⁰⁹⁹¹ is an apocalyptic number.

780991 is a deficient number, since it is larger than the sum of its proper divisors (1).

780991 is an equidigital number, since it uses as much as digits as its factorization.

780991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4536, while the sum is 34.

The square root of 780991 is about 883.7369518132. The cubic root of 780991 is about 92.0906085901.

It can be divided in two parts, 780 and 991, that added together give a palindrome (1771).

The spelling of 780991 in words is "seven hundred eighty thousand, nine hundred ninety-one".