680721557 has 2 divisors, whose sum is σ = 680721558. Its totient is φ = 680721556.

The previous prime is 680721511. The next prime is 680721571. The reversal of 680721557 is 755127086.

680721557 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 413268241 + 267453316 = 20329^2 + 16354^2 .

It is a cyclic number.

It is not a de Polignac number, because 680721557 - 2¹⁴ = 680705173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (680721757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340360778 + 340360779.

It is an arithmetic number, because the mean of its divisors is an integer number (340360779).

Almost surely, 2^680721557 is an apocalyptic number.

It is an amenable number.

680721557 is a deficient number, since it is larger than the sum of its proper divisors (1).

680721557 is an equidigital number, since it uses as much as digits as its factorization.

680721557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 117600, while the sum is 41.

The square root of 680721557 is about 26090.6411764832. The cubic root of 680721557 is about 879.6768600923.

The spelling of 680721557 in words is "six hundred eighty million, seven hundred twenty-one thousand, five hundred fifty-seven".