685631 has 2 divisors, whose sum is σ = 685632. Its totient is φ = 685630.

The previous prime is 685621. The next prime is 685637. The reversal of 685631 is 136586.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 685631 - 2¹⁴ = 669247 is a prime.

It is a super-2 number, since 2×685631² = 940179736322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 685594 and 685603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685637) 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 as a sum of consecutive naturals, namely, 342815 + 342816.

It is an arithmetic number, because the mean of its divisors is an integer number (342816).

2⁶⁸⁵⁶³¹ is an apocalyptic number.

685631 is a deficient number, since it is larger than the sum of its proper divisors (1).

685631 is an equidigital number, since it uses as much as digits as its factorization.

685631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 685631 is about 828.0283811561. The cubic root of 685631 is about 88.1786573617.

The spelling of 685631 in words is "six hundred eighty-five thousand, six hundred thirty-one".