781631 has 2 divisors, whose sum is σ = 781632. Its totient is φ = 781630.

The previous prime is 781619. The next prime is 781633. The reversal of 781631 is 136187.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 781631 - 2⁶ = 781567 is a prime.

It is a super-2 number, since 2×781631² = 1221894040322, which contains 22 as substring.

Together with 781633, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 781631.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (781633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390815 + 390816.

It is an arithmetic number, because the mean of its divisors is an integer number (390816).

2⁷⁸¹⁶³¹ is an apocalyptic number.

781631 is a deficient number, since it is larger than the sum of its proper divisors (1).

781631 is an equidigital number, since it uses as much as digits as its factorization.

781631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 26.

The square root of 781631 is about 884.0989763595. The cubic root of 781631 is about 92.1157569368.

The spelling of 781631 in words is "seven hundred eighty-one thousand, six hundred thirty-one".