681455809 has 2 divisors, whose sum is σ = 681455810. Its totient is φ = 681455808.

The previous prime is 681455777. The next prime is 681455837. The reversal of 681455809 is 908554186.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 530288784 + 151167025 = 23028^2 + 12295^2 .

It is a cyclic number.

It is not a de Polignac number, because 681455809 - 2⁵ = 681455777 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (681455839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340727904 + 340727905.

It is an arithmetic number, because the mean of its divisors is an integer number (340727905).

Almost surely, 2^681455809 is an apocalyptic number.

It is an amenable number.

681455809 is a deficient number, since it is larger than the sum of its proper divisors (1).

681455809 is an equidigital number, since it uses as much as digits as its factorization.

681455809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 345600, while the sum is 46.

The square root of 681455809 is about 26104.7085599514. The cubic root of 681455809 is about 879.9930306783.

It can be divided in two parts, 681 and 455809, that added together give a triangular number (456490 = T₉₅₅).

The spelling of 681455809 in words is "six hundred eighty-one million, four hundred fifty-five thousand, eight hundred nine".