644834 has 4 divisors (see below), whose sum is σ = 967254. Its totient is φ = 322416.

The previous prime is 644801. The next prime is 644837. The reversal of 644834 is 438446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 438446 = 2 ⋅219223.

It can be written as a sum of positive squares in only one way, i.e., 644809 + 25 = 803^2 + 5^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644797 and 644806.

It is not an unprimeable number, because it can be changed into a prime (644837) 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 as a sum of consecutive naturals, namely, 161207 + ... + 161210.

2⁶⁴⁴⁸³⁴ is an apocalyptic number.

644834 is a deficient number, since it is larger than the sum of its proper divisors (322420).

644834 is a wasteful number, since it uses less digits than its factorization.

644834 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322419.

The product of its digits is 9216, while the sum is 29.

The square root of 644834 is about 803.0155664743. The cubic root of 644834 is about 86.3938131429.

The spelling of 644834 in words is "six hundred forty-four thousand, eight hundred thirty-four".