644945 has 8 divisors (see below), whose sum is σ = 884544. Its totient is φ = 442224.

The previous prime is 644933. The next prime is 644951. The reversal of 644945 is 549446.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644945 - 2⁶ = 644881 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 9179 + ... + 9248.

It is an arithmetic number, because the mean of its divisors is an integer number (110568).

2⁶⁴⁴⁹⁴⁵ is an apocalyptic number.

It is an amenable number.

644945 is a deficient number, since it is larger than the sum of its proper divisors (239599).

644945 is a wasteful number, since it uses less digits than its factorization.

644945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18439.

The product of its digits is 17280, while the sum is 32.

The square root of 644945 is about 803.0846779761. The cubic root of 644945 is about 86.3987700585.

The spelling of 644945 in words is "six hundred forty-four thousand, nine hundred forty-five".