681557 has 2 divisors, whose sum is σ = 681558. Its totient is φ = 681556.

The previous prime is 681539. The next prime is 681563. The reversal of 681557 is 755186.

681557 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 361201 + 320356 = 601^2 + 566^2 .

It is a cyclic number.

It is not a de Polignac number, because 681557 - 2⁶ = 681493 is a prime.

It is a Chen prime.

It is a nialpdrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340778 + 340779.

It is an arithmetic number, because the mean of its divisors is an integer number (340779).

2⁶⁸¹⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

681557 is a deficient number, since it is larger than the sum of its proper divisors (1).

681557 is an equidigital number, since it uses as much as digits as its factorization.

681557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 32.

The square root of 681557 is about 825.5646552512. The cubic root of 681557 is about 88.0036585944.

The spelling of 681557 in words is "six hundred eighty-one thousand, five hundred fifty-seven".