681657 has 4 divisors (see below), whose sum is σ = 908880. Its totient is φ = 454436.

The previous prime is 681647. The next prime is 681673. The reversal of 681657 is 756186.

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 681657 - 2¹⁰ = 680633 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (681607) 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 3 ways as a sum of consecutive naturals, for example, 113607 + ... + 113612.

It is an arithmetic number, because the mean of its divisors is an integer number (227220).

2⁶⁸¹⁶⁵⁷ is an apocalyptic number.

It is an amenable number.

681657 is a deficient number, since it is larger than the sum of its proper divisors (227223).

681657 is a wasteful number, since it uses less digits than its factorization.

681657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 227222.

The product of its digits is 10080, while the sum is 33.

The square root of 681657 is about 825.6252176381. The cubic root of 681657 is about 88.0079624338.

Subtracting 681657 from its reverse (756186), we obtain a square (74529 = 273²).

The spelling of 681657 in words is "six hundred eighty-one thousand, six hundred fifty-seven".