687881561 has 2 divisors, whose sum is σ = 687881562. Its totient is φ = 687881560.

The previous prime is 687881543. The next prime is 687881587. The reversal of 687881561 is 165188786.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 446265625 + 241615936 = 21125^2 + 15544^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-687881561 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (687881501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343940780 + 343940781.

It is an arithmetic number, because the mean of its divisors is an integer number (343940781).

Almost surely, 2^687881561 is an apocalyptic number.

It is an amenable number.

687881561 is a deficient number, since it is larger than the sum of its proper divisors (1).

687881561 is an equidigital number, since it uses as much as digits as its factorization.

687881561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 645120, while the sum is 50.

The square root of 687881561 is about 26227.4962777616. The cubic root of 687881561 is about 882.7503316031.

The spelling of 687881561 in words is "six hundred eighty-seven million, eight hundred eighty-one thousand, five hundred sixty-one".