644537 has 4 divisors (see below), whose sum is σ = 678480. Its totient is φ = 610596.

The previous prime is 644531. The next prime is 644549. The reversal of 644537 is 735446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644537 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644537.

It is not an unprimeable number, because it can be changed into a prime (644531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16943 + ... + 16980.

It is an arithmetic number, because the mean of its divisors is an integer number (169620).

2⁶⁴⁴⁵³⁷ is an apocalyptic number.

It is an amenable number.

644537 is a deficient number, since it is larger than the sum of its proper divisors (33943).

644537 is a wasteful number, since it uses less digits than its factorization.

644537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33942.

The product of its digits is 10080, while the sum is 29.

The square root of 644537 is about 802.8306172537. The cubic root of 644537 is about 86.3805472467.

Subtracting 644537 from its reverse (735446), we obtain a palindrome (90909).

The spelling of 644537 in words is "six hundred forty-four thousand, five hundred thirty-seven".