643842169 has 2 divisors, whose sum is σ = 643842170. Its totient is φ = 643842168.

The previous prime is 643842107. The next prime is 643842223. The reversal of 643842169 is 961248346.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 514155625 + 129686544 = 22675^2 + 11388^2 .

It is a cyclic number.

It is not a de Polignac number, because 643842169 - 2¹³ = 643833977 is a prime.

It is a super-2 number, since 2×643842169² = 829065477165249122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (643843169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321921084 + 321921085.

It is an arithmetic number, because the mean of its divisors is an integer number (321921085).

Almost surely, 2^643842169 is an apocalyptic number.

It is an amenable number.

643842169 is a deficient number, since it is larger than the sum of its proper divisors (1).

643842169 is an equidigital number, since it uses as much as digits as its factorization.

643842169 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 248832, while the sum is 43.

The square root of 643842169 is about 25374.0451840064. The cubic root of 643842169 is about 863.4949577731.

The spelling of 643842169 in words is "six hundred forty-three million, eight hundred forty-two thousand, one hundred sixty-nine".