644987429 has 4 divisors (see below), whose sum is σ = 682927884. Its totient is φ = 607046976.

The previous prime is 644987411. The next prime is 644987437. The reversal of 644987429 is 924789446.

644987429 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 432556804 + 212430625 = 20798^2 + 14575^2 .

It is a cyclic number.

It is not a de Polignac number, because 644987429 - 2²⁴ = 628210213 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644987479) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18970202 + ... + 18970235.

It is an arithmetic number, because the mean of its divisors is an integer number (170731971).

Almost surely, 2^644987429 is an apocalyptic number.

It is an amenable number.

644987429 is a deficient number, since it is larger than the sum of its proper divisors (37940455).

644987429 is a wasteful number, since it uses less digits than its factorization.

644987429 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37940454.

The product of its digits is 3483648, while the sum is 53.

The square root of 644987429 is about 25396.6027058739. The cubic root of 644987429 is about 864.0066465574.

The spelling of 644987429 in words is "six hundred forty-four million, nine hundred eighty-seven thousand, four hundred twenty-nine".