691731 has 12 divisors (see below), whose sum is σ = 1007760. Its totient is φ = 457200.

The previous prime is 691729. The next prime is 691739. The reversal of 691731 is 137196.

It is not a de Polignac number, because 691731 - 2¹ = 691729 is a prime.

It is a super-2 number, since 2×691731² = 956983552722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 691695 and 691704.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 691731.

It is not an unprimeable number, because it can be changed into a prime (691739) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1105 + ... + 1613.

It is an arithmetic number, because the mean of its divisors is an integer number (83980).

2⁶⁹¹⁷³¹ is an apocalyptic number.

691731 is a deficient number, since it is larger than the sum of its proper divisors (316029).

691731 is a wasteful number, since it uses less digits than its factorization.

691731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 666 (or 663 counting only the distinct ones).

The product of its digits is 1134, while the sum is 27.

The square root of 691731 is about 831.7036731914. The cubic root of 691731 is about 88.4393916155.

The spelling of 691731 in words is "six hundred ninety-one thousand, seven hundred thirty-one".