681671509 has 2 divisors, whose sum is σ = 681671510. Its totient is φ = 681671508.

The previous prime is 681671449. The next prime is 681671513. The reversal of 681671509 is 905176186.

It is a happy number.

681671509 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., 546530884 + 135140625 = 23378^2 + 11625^2 .

It is a cyclic number.

It is not a de Polignac number, because 681671509 - 2¹³ = 681663317 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681671579) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340835754 + 340835755.

It is an arithmetic number, because the mean of its divisors is an integer number (340835755).

Almost surely, 2^681671509 is an apocalyptic number.

It is an amenable number.

681671509 is a deficient number, since it is larger than the sum of its proper divisors (1).

681671509 is an equidigital number, since it uses as much as digits as its factorization.

681671509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90720, while the sum is 43.

The square root of 681671509 is about 26108.8396716514. The cubic root of 681671509 is about 880.0858684287.

The spelling of 681671509 in words is "six hundred eighty-one million, six hundred seventy-one thousand, five hundred nine".