643129969 has 2 divisors, whose sum is σ = 643129970. Its totient is φ = 643129968.

The previous prime is 643129961. The next prime is 643129987. The reversal of 643129969 is 969921346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 641963569 + 1166400 = 25337^2 + 1080^2 .

It is a cyclic number.

It is not a de Polignac number, because 643129969 - 2³ = 643129961 is a prime.

It is a super-2 number, since 2×643129969² = 827232314051881922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (643129961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321564984 + 321564985.

It is an arithmetic number, because the mean of its divisors is an integer number (321564985).

Almost surely, 2^643129969 is an apocalyptic number.

It is an amenable number.

643129969 is a deficient number, since it is larger than the sum of its proper divisors (1).

643129969 is an equidigital number, since it uses as much as digits as its factorization.

643129969 is an evil number, because the sum of its binary digits is even.

The product of its digits is 629856, while the sum is 49.

The square root of 643129969 is about 25360.0072752355. The cubic root of 643129969 is about 863.1764490680.

The spelling of 643129969 in words is "six hundred forty-three million, one hundred twenty-nine thousand, nine hundred sixty-nine".