681516557 has 4 divisors (see below), whose sum is σ = 681610716. Its totient is φ = 681422400.

The previous prime is 681516547. The next prime is 681516581. The reversal of 681516557 is 755615186.

It is a happy number.

681516557 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 173870596 + 507645961 = 13186^2 + 22531^2 .

It is a cyclic number.

It is not a de Polignac number, because 681516557 - 2⁴ = 681516541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681516527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35228 + ... + 51029.

It is an arithmetic number, because the mean of its divisors is an integer number (170402679).

Almost surely, 2^681516557 is an apocalyptic number.

It is an amenable number.

681516557 is a deficient number, since it is larger than the sum of its proper divisors (94159).

681516557 is an equidigital number, since it uses as much as digits as its factorization.

681516557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94158.

The product of its digits is 252000, while the sum is 44.

The square root of 681516557 is about 26105.8720789021. The cubic root of 681516557 is about 880.0191787315.

The spelling of 681516557 in words is "six hundred eighty-one million, five hundred sixteen thousand, five hundred fifty-seven".