688561 has 2 divisors, whose sum is σ = 688562. Its totient is φ = 688560.

The previous prime is 688543. The next prime is 688573. The reversal of 688561 is 165886.

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., 664225 + 24336 = 815^2 + 156^2 .

It is a cyclic number.

It is not a de Polignac number, because 688561 - 2⁷ = 688433 is a prime.

688561 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (688511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344280 + 344281.

It is an arithmetic number, because the mean of its divisors is an integer number (344281).

2⁶⁸⁸⁵⁶¹ is an apocalyptic number.

It is an amenable number.

688561 is a deficient number, since it is larger than the sum of its proper divisors (1).

688561 is an equidigital number, since it uses as much as digits as its factorization.

688561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11520, while the sum is 34.

The square root of 688561 is about 829.7957580031. The cubic root of 688561 is about 88.3040874662.

The spelling of 688561 in words is "six hundred eighty-eight thousand, five hundred sixty-one".