644571 has 8 divisors (see below), whose sum is σ = 954960. Its totient is φ = 429696.

The previous prime is 644569. The next prime is 644593. The reversal of 644571 is 175446.

It is not a de Polignac number, because 644571 - 2¹ = 644569 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 23873 = 644571 / (6 + 4 + 4 + 5 + 7 + 1).

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

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11910 + ... + 11963.

It is an arithmetic number, because the mean of its divisors is an integer number (119370).

2⁶⁴⁴⁵⁷¹ is an apocalyptic number.

644571 is a deficient number, since it is larger than the sum of its proper divisors (310389).

644571 is a wasteful number, since it uses less digits than its factorization.

644571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23882 (or 23876 counting only the distinct ones).

The product of its digits is 3360, while the sum is 27.

The square root of 644571 is about 802.8517920513. The cubic root of 644571 is about 86.3820661080.

The spelling of 644571 in words is "six hundred forty-four thousand, five hundred seventy-one".