781220761 has 2 divisors, whose sum is σ = 781220762. Its totient is φ = 781220760.

The previous prime is 781220753. The next prime is 781220779. The reversal of 781220761 is 167022187.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 709902736 + 71318025 = 26644^2 + 8445^2 .

It is a cyclic number.

It is not a de Polignac number, because 781220761 - 2³ = 781220753 is a prime.

It is a super-2 number, since 2×781220761² = 1220611754834838242, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (781220731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390610380 + 390610381.

It is an arithmetic number, because the mean of its divisors is an integer number (390610381).

Almost surely, 2^781220761 is an apocalyptic number.

It is an amenable number.

781220761 is a deficient number, since it is larger than the sum of its proper divisors (1).

781220761 is an equidigital number, since it uses as much as digits as its factorization.

781220761 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9408, while the sum is 34.

The square root of 781220761 is about 27950.3266707207. The cubic root of 781220761 is about 920.9963846611.

The spelling of 781220761 in words is "seven hundred eighty-one million, two hundred twenty thousand, seven hundred sixty-one".