643566 has 48 divisors (see below), whose sum is σ = 1641600. Its totient is φ = 166320.

The previous prime is 643553. The next prime is 643567. The reversal of 643566 is 665346.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643567) by changing a digit.

643566 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3135 + ... + 3333.

It is an arithmetic number, because the mean of its divisors is an integer number (34200).

2⁶⁴³⁵⁶⁶ is an apocalyptic number.

643566 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 643566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (820800).

643566 is an abundant number, since it is smaller than the sum of its proper divisors (998034).

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

643566 is a wasteful number, since it uses less digits than its factorization.

643566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 229 (or 222 counting only the distinct ones).

The product of its digits is 12960, while the sum is 30.

The square root of 643566 is about 802.2256540401. The cubic root of 643566 is about 86.3371477902.

The spelling of 643566 in words is "six hundred forty-three thousand, five hundred sixty-six".