687731 has 8 divisors (see below), whose sum is σ = 758784. Its totient is φ = 618120.

The previous prime is 687721. The next prime is 687737. The reversal of 687731 is 137786.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-687731 is a prime.

It is a super-2 number, since 2×687731² = 945947856722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687737) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 830 + ... + 1436.

It is an arithmetic number, because the mean of its divisors is an integer number (94848).

2⁶⁸⁷⁷³¹ is an apocalyptic number.

687731 is a deficient number, since it is larger than the sum of its proper divisors (71053).

687731 is a wasteful number, since it uses less digits than its factorization.

687731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 721.

The product of its digits is 7056, while the sum is 32.

The square root of 687731 is about 829.2954841310. The cubic root of 687731 is about 88.2685922516.

Subtracting from 687731 its reverse (137786), we obtain a palindrome (549945).

The spelling of 687731 in words is "six hundred eighty-seven thousand, seven hundred thirty-one".