681631 has 2 divisors, whose sum is σ = 681632. Its totient is φ = 681630.

The previous prime is 681623. The next prime is 681647. The reversal of 681631 is 136186.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 681631 - 2³ = 681623 is a prime.

It is a super-2 number, since 2×681631² = 929241640322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 681596 and 681605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340815 + 340816.

It is an arithmetic number, because the mean of its divisors is an integer number (340816).

2⁶⁸¹⁶³¹ is an apocalyptic number.

681631 is a deficient number, since it is larger than the sum of its proper divisors (1).

681631 is an equidigital number, since it uses as much as digits as its factorization.

681631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 25.

The square root of 681631 is about 825.6094718449. The cubic root of 681631 is about 88.0068434761.

The spelling of 681631 in words is "six hundred eighty-one thousand, six hundred thirty-one".