644623 has 8 divisors (see below), whose sum is σ = 780192. Its totient is φ = 519936.

The previous prime is 644617. The next prime is 644629. The reversal of 644623 is 326446.

It is an interprime number because it is at equal distance from previous prime (644617) and next prime (644629).

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644623 is a prime.

644623 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644629) 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 7 ways as a sum of consecutive naturals, for example, 2590 + ... + 2827.

It is an arithmetic number, because the mean of its divisors is an integer number (97524).

2⁶⁴⁴⁶²³ is an apocalyptic number.

644623 is a deficient number, since it is larger than the sum of its proper divisors (135569).

644623 is a wasteful number, since it uses less digits than its factorization.

644623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5441.

The product of its digits is 3456, while the sum is 25.

The square root of 644623 is about 802.8841759557. The cubic root of 644623 is about 86.3843889691.

The spelling of 644623 in words is "six hundred forty-four thousand, six hundred twenty-three".