644917 has 16 divisors (see below), whose sum is σ = 837760. Its totient is φ = 482112.

The previous prime is 644911. The next prime is 644923. The reversal of 644917 is 719446.

It is an interprime number because it is at equal distance from previous prime (644911) and next prime (644923).

It is a cyclic number.

It is not a de Polignac number, because 644917 - 2³ = 644909 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1543 + ... + 1915.

It is an arithmetic number, because the mean of its divisors is an integer number (52360).

2⁶⁴⁴⁹¹⁷ is an apocalyptic number.

It is an amenable number.

644917 is a deficient number, since it is larger than the sum of its proper divisors (192843).

644917 is a wasteful number, since it uses less digits than its factorization.

644917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412.

The product of its digits is 6048, while the sum is 31.

The square root of 644917 is about 803.0672450050. The cubic root of 644917 is about 86.3975197190.

Subtracting 644917 from its reverse (719446), we obtain a square (74529 = 273²).

The spelling of 644917 in words is "six hundred forty-four thousand, nine hundred seventeen".