643663829 has 2 divisors, whose sum is σ = 643663830. Its totient is φ = 643663828.

The previous prime is 643663751. The next prime is 643663837. The reversal of 643663829 is 928366346.

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., 341251729 + 302412100 = 18473^2 + 17390^2 .

It is a cyclic number.

It is not a de Polignac number, because 643663829 - 2²⁴ = 626886613 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643693829) 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, 321831914 + 321831915.

It is an arithmetic number, because the mean of its divisors is an integer number (321831915).

Almost surely, 2^643663829 is an apocalyptic number.

It is an amenable number.

643663829 is a deficient number, since it is larger than the sum of its proper divisors (1).

643663829 is an equidigital number, since it uses as much as digits as its factorization.

643663829 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1119744, while the sum is 47.

The square root of 643663829 is about 25370.5307197150. The cubic root of 643663829 is about 863.4152229567.

The spelling of 643663829 in words is "six hundred forty-three million, six hundred sixty-three thousand, eight hundred twenty-nine".