644826829 has 4 divisors (see below), whose sum is σ = 645301980. Its totient is φ = 644351680.

The previous prime is 644826823. The next prime is 644826841. The reversal of 644826829 is 928628446.

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 298494729 + 346332100 = 17277^2 + 18610^2 .

It is a cyclic number.

It is not a de Polignac number, because 644826829 - 2⁵ = 644826797 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644826823) 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, 235534 + ... + 238255.

It is an arithmetic number, because the mean of its divisors is an integer number (161325495).

Almost surely, 2^644826829 is an apocalyptic number.

It is an amenable number.

644826829 is a deficient number, since it is larger than the sum of its proper divisors (475151).

644826829 is a wasteful number, since it uses less digits than its factorization.

644826829 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475150.

The product of its digits is 1327104, while the sum is 49.

The square root of 644826829 is about 25393.4406688026. The cubic root of 644826829 is about 863.9349288878.

The spelling of 644826829 in words is "six hundred forty-four million, eight hundred twenty-six thousand, eight hundred twenty-nine".