643531769 has 2 divisors, whose sum is σ = 643531770. Its totient is φ = 643531768.

The previous prime is 643531751. The next prime is 643531771. The reversal of 643531769 is 967135346.

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., 643281769 + 250000 = 25363^2 + 500^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643531769 is a prime.

It is a super-2 number, since 2×643531769² = 828266275424538722, which contains 22 as substring.

Together with 643531771, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (643531799) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321765884 + 321765885.

It is an arithmetic number, because the mean of its divisors is an integer number (321765885).

Almost surely, 2^643531769 is an apocalyptic number.

It is an amenable number.

643531769 is a deficient number, since it is larger than the sum of its proper divisors (1).

643531769 is an equidigital number, since it uses as much as digits as its factorization.

643531769 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 408240, while the sum is 44.

The square root of 643531769 is about 25367.9279603203. The cubic root of 643531769 is about 863.3561701778.

The spelling of 643531769 in words is "six hundred forty-three million, five hundred thirty-one thousand, seven hundred sixty-nine".