681637 has 4 divisors (see below), whose sum is σ = 743616. Its totient is φ = 619660.

The previous prime is 681631. The next prime is 681647. The reversal of 681637 is 736186.

681637 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 681637 - 2¹⁹ = 157349 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 681599 and 681608.

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 polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30973 + ... + 30994.

It is an arithmetic number, because the mean of its divisors is an integer number (185904).

2⁶⁸¹⁶³⁷ is an apocalyptic number.

It is an amenable number.

681637 is a deficient number, since it is larger than the sum of its proper divisors (61979).

681637 is a wasteful number, since it uses less digits than its factorization.

681637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61978.

The product of its digits is 6048, while the sum is 31.

The square root of 681637 is about 825.6131055161. The cubic root of 681637 is about 88.0071016996.

The spelling of 681637 in words is "six hundred eighty-one thousand, six hundred thirty-seven".