691631 has 2 divisors, whose sum is σ = 691632. Its totient is φ = 691630.

The previous prime is 691591. The next prime is 691637. The reversal of 691631 is 136196.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 691631 - 2¹⁰ = 690607 is a prime.

It is a super-2 number, since 2×691631² = 956706880322, which contains 22 as substring.

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 691631.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 691631.

It is not a weakly prime, because it can be changed into another prime (691637) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345815 + 345816.

It is an arithmetic number, because the mean of its divisors is an integer number (345816).

2⁶⁹¹⁶³¹ is an apocalyptic number.

691631 is a deficient number, since it is larger than the sum of its proper divisors (1).

691631 is an equidigital number, since it uses as much as digits as its factorization.

691631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 972, while the sum is 26.

The square root of 691631 is about 831.6435534530. The cubic root of 691631 is about 88.4351296671.

The spelling of 691631 in words is "six hundred ninety-one thousand, six hundred thirty-one".