168991309 has 2 divisors, whose sum is σ = 168991310. Its totient is φ = 168991308.

The previous prime is 168991297. The next prime is 168991313. The reversal of 168991309 is 903199861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 135606025 + 33385284 = 11645^2 + 5778^2 .

It is an emirp because it is prime and its reverse (903199861) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-168991309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (168991409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 84495654 + 84495655.

It is an arithmetic number, because the mean of its divisors is an integer number (84495655).

Almost surely, 2^168991309 is an apocalyptic number.

It is an amenable number.

168991309 is a deficient number, since it is larger than the sum of its proper divisors (1).

168991309 is an equidigital number, since it uses as much as digits as its factorization.

168991309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 104976, while the sum is 46.

The square root of 168991309 is about 12999.6657264716. The cubic root of 168991309 is about 552.8680037731.

The spelling of 168991309 in words is "one hundred sixty-eight million, nine hundred ninety-one thousand, three hundred nine".