644429 has 4 divisors (see below), whose sum is σ = 661884. Its totient is φ = 626976.

The previous prime is 644411. The next prime is 644431. The reversal of 644429 is 924446.

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 592900 + 51529 = 770^2 + 227^2 .

It is a cyclic number.

It is not a de Polignac number, because 644429 - 2⁸ = 644173 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644489) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8672 + ... + 8745.

It is an arithmetic number, because the mean of its divisors is an integer number (165471).

2⁶⁴⁴⁴²⁹ is an apocalyptic number.

It is an amenable number.

644429 is a deficient number, since it is larger than the sum of its proper divisors (17455).

644429 is a wasteful number, since it uses less digits than its factorization.

644429 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17454.

The product of its digits is 6912, while the sum is 29.

The square root of 644429 is about 802.7633524271. The cubic root of 644429 is about 86.3757222740.

The spelling of 644429 in words is "six hundred forty-four thousand, four hundred twenty-nine".