687668621 has 2 divisors, whose sum is σ = 687668622. Its totient is φ = 687668620.

The previous prime is 687668617. The next prime is 687668669. The reversal of 687668621 is 126866786.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 678602500 + 9066121 = 26050^2 + 3011^2 .

It is a cyclic number.

It is not a de Polignac number, because 687668621 - 2² = 687668617 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 687668621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687661621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343834310 + 343834311.

It is an arithmetic number, because the mean of its divisors is an integer number (343834311).

Almost surely, 2^687668621 is an apocalyptic number.

It is an amenable number.

687668621 is a deficient number, since it is larger than the sum of its proper divisors (1).

687668621 is an equidigital number, since it uses as much as digits as its factorization.

687668621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1161216, while the sum is 50.

The square root of 687668621 is about 26223.4364834207. The cubic root of 687668621 is about 882.6592344018.

The spelling of 687668621 in words is "six hundred eighty-seven million, six hundred sixty-eight thousand, six hundred twenty-one".