644040632129 has 4 divisors (see below), whose sum is σ = 644048539860. Its totient is φ = 644032724400.

The previous prime is 644040632051. The next prime is 644040632161. The reversal of 644040632129 is 921236040446.

It is a happy number.

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 161395027600 + 482645604529 = 401740^2 + 694727^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644040632129 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644040632629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3830414 + ... + 3995015.

It is an arithmetic number, because the mean of its divisors is an integer number (161012134965).

Almost surely, 2^644040632129 is an apocalyptic number.

It is an amenable number.

644040632129 is a deficient number, since it is larger than the sum of its proper divisors (7907731).

644040632129 is an equidigital number, since it uses as much as digits as its factorization.

644040632129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7907730.

The product of its (nonzero) digits is 248832, while the sum is 41.

The spelling of 644040632129 in words is "six hundred forty-four billion, forty million, six hundred thirty-two thousand, one hundred twenty-nine".