687581 has 2 divisors, whose sum is σ = 687582. Its totient is φ = 687580.

The previous prime is 687559. The next prime is 687593. The reversal of 687581 is 185786.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 502681 + 184900 = 709^2 + 430^2 .

It is a cyclic number.

It is not a de Polignac number, because 687581 - 2⁶ = 687517 is a prime.

It is a super-2 number, since 2×687581² = 945535263122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343790 + 343791.

It is an arithmetic number, because the mean of its divisors is an integer number (343791).

2⁶⁸⁷⁵⁸¹ is an apocalyptic number.

It is an amenable number.

687581 is a deficient number, since it is larger than the sum of its proper divisors (1).

687581 is an equidigital number, since it uses as much as digits as its factorization.

687581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13440, while the sum is 35.

The square root of 687581 is about 829.2050409881. The cubic root of 687581 is about 88.2621744072.

The spelling of 687581 in words is "six hundred eighty-seven thousand, five hundred eighty-one".