687931 has 2 divisors, whose sum is σ = 687932. Its totient is φ = 687930.

The previous prime is 687923. The next prime is 687949. The reversal of 687931 is 139786.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 687931 - 2³ = 687923 is a prime.

It is a super-2 number, since 2×687931² = 946498121522, which contains 22 as substring.

687931 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (687901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343965 + 343966.

It is an arithmetic number, because the mean of its divisors is an integer number (343966).

2⁶⁸⁷⁹³¹ is an apocalyptic number.

687931 is a deficient number, since it is larger than the sum of its proper divisors (1).

687931 is an equidigital number, since it uses as much as digits as its factorization.

687931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 34.

The square root of 687931 is about 829.4160596468. The cubic root of 687931 is about 88.2771479259.

The spelling of 687931 in words is "six hundred eighty-seven thousand, nine hundred thirty-one".