168721517309 has 2 divisors, whose sum is σ = 168721517310. Its totient is φ = 168721517308.

The previous prime is 168721517297. The next prime is 168721517387. The reversal of 168721517309 is 903715127861.

It is a happy number.

168721517309 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 152370780409 + 16350736900 = 390347^2 + 127870^2 .

It is a cyclic number.

It is not a de Polignac number, because 168721517309 - 2⁸ = 168721517053 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (168721517509) 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, 84360758654 + 84360758655.

It is an arithmetic number, because the mean of its divisors is an integer number (84360758655).

Almost surely, 2^168721517309 is an apocalyptic number.

It is an amenable number.

168721517309 is a deficient number, since it is larger than the sum of its proper divisors (1).

168721517309 is an equidigital number, since it uses as much as digits as its factorization.

168721517309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 635040, while the sum is 50.

The spelling of 168721517309 in words is "one hundred sixty-eight billion, seven hundred twenty-one million, five hundred seventeen thousand, three hundred nine".