643661129 has 4 divisors (see below), whose sum is σ = 645952020. Its totient is φ = 641370240.

The previous prime is 643661107. The next prime is 643661131. The reversal of 643661129 is 921166346.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 283989904 + 359671225 = 16852^2 + 18965^2 .

It is a cyclic number.

It is not a de Polignac number, because 643661129 - 2¹² = 643657033 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643661092 and 643661101.

It is not an unprimeable number, because it can be changed into a prime (643661189) 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 in 3 ways as a sum of consecutive naturals, for example, 1145024 + ... + 1145585.

It is an arithmetic number, because the mean of its divisors is an integer number (161488005).

Almost surely, 2^643661129 is an apocalyptic number.

It is an amenable number.

643661129 is a deficient number, since it is larger than the sum of its proper divisors (2290891).

643661129 is a wasteful number, since it uses less digits than its factorization.

643661129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2290890.

The product of its digits is 46656, while the sum is 38.

The square root of 643661129 is about 25370.4775083166. The cubic root of 643661129 is about 863.4140156886.

The spelling of 643661129 in words is "six hundred forty-three million, six hundred sixty-one thousand, one hundred twenty-nine".