643996169 has 2 divisors, whose sum is σ = 643996170. Its totient is φ = 643996168.

The previous prime is 643996147. The next prime is 643996187. The reversal of 643996169 is 961699346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 400480144 + 243516025 = 20012^2 + 15605^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643996169 is a prime.

It is a super-2 number, since 2×643996169² = 829462131373353122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 643996169.

It is not a weakly prime, because it can be changed into another prime (643996189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321998084 + 321998085.

It is an arithmetic number, because the mean of its divisors is an integer number (321998085).

Almost surely, 2^643996169 is an apocalyptic number.

It is an amenable number.

643996169 is a deficient number, since it is larger than the sum of its proper divisors (1).

643996169 is an equidigital number, since it uses as much as digits as its factorization.

643996169 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1889568, while the sum is 53.

The square root of 643996169 is about 25377.0795995126. The cubic root of 643996169 is about 863.5637984658.

The spelling of 643996169 in words is "six hundred forty-three million, nine hundred ninety-six thousand, one hundred sixty-nine".