643660331 has 2 divisors, whose sum is σ = 643660332. Its totient is φ = 643660330.

The previous prime is 643660327. The next prime is 643660343. The reversal of 643660331 is 133066346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643660331 - 2² = 643660327 is a prime.

It is a super-2 number, since 2×643660331² = 828597243406059122, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (643660931) 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, 321830165 + 321830166.

It is an arithmetic number, because the mean of its divisors is an integer number (321830166).

Almost surely, 2^643660331 is an apocalyptic number.

643660331 is a deficient number, since it is larger than the sum of its proper divisors (1).

643660331 is an equidigital number, since it uses as much as digits as its factorization.

643660331 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 32.

The square root of 643660331 is about 25370.4617813709. The cubic root of 643660331 is about 863.4136588732.

The spelling of 643660331 in words is "six hundred forty-three million, six hundred sixty thousand, three hundred thirty-one".