644166 has 32 divisors (see below), whose sum is σ = 1459200. Its totient is φ = 210600.

The previous prime is 644159. The next prime is 644173. The reversal of 644166 is 661446.

644166 is a `hidden beast` number, since 644 + 16 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (644159) and next prime (644173).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4191 + ... + 4341.

It is an arithmetic number, because the mean of its divisors is an integer number (45600).

2⁶⁴⁴¹⁶⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644166, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (729600).

644166 is an abundant number, since it is smaller than the sum of its proper divisors (815034).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644166 is a wasteful number, since it uses less digits than its factorization.

644166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241 (or 235 counting only the distinct ones).

The product of its digits is 3456, while the sum is 27.

The square root of 644166 is about 802.5995265386. The cubic root of 644166 is about 86.3639703168.

The spelling of 644166 in words is "six hundred forty-four thousand, one hundred sixty-six".