691931 has 2 divisors, whose sum is σ = 691932. Its totient is φ = 691930.

The previous prime is 691921. The next prime is 691949. The reversal of 691931 is 139196.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691931 is a prime.

It is a super-2 number, since 2×691931² = 957537017522, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 691894 and 691903.

It is not a weakly prime, because it can be changed into another prime (691921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345965 + 345966.

It is an arithmetic number, because the mean of its divisors is an integer number (345966).

2⁶⁹¹⁹³¹ is an apocalyptic number.

691931 is a deficient number, since it is larger than the sum of its proper divisors (1).

691931 is an equidigital number, since it uses as much as digits as its factorization.

691931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1458, while the sum is 29.

The square root of 691931 is about 831.8238996326. The cubic root of 691931 is about 88.4479142801.

The spelling of 691931 in words is "six hundred ninety-one thousand, nine hundred thirty-one".