681639 has 12 divisors (see below), whose sum is σ = 1057464. Its totient is φ = 389424.

The previous prime is 681631. The next prime is 681647. The reversal of 681639 is 936186.

It is an interprime number because it is at equal distance from previous prime (681631) and next prime (681647).

It is not a de Polignac number, because 681639 - 2³ = 681631 is a prime.

It is a super-3 number, since 3×681639³ = 950133315893160357, which contains 333 as substring.

681639 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2172 + ... + 2465.

It is an arithmetic number, because the mean of its divisors is an integer number (88122).

2⁶⁸¹⁶³⁹ is an apocalyptic number.

681639 is a deficient number, since it is larger than the sum of its proper divisors (375825).

681639 is a wasteful number, since it uses less digits than its factorization.

681639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4654 (or 4647 counting only the distinct ones).

The product of its digits is 7776, while the sum is 33.

The square root of 681639 is about 825.6143167363. The cubic root of 681639 is about 88.0071877738.

The spelling of 681639 in words is "six hundred eighty-one thousand, six hundred thirty-nine".