221643 has 8 divisors (see below), whose sum is σ = 328400. Its totient is φ = 147744.

The previous prime is 221623. The next prime is 221653. The reversal of 221643 is 346122.

It is a happy number.

221643 is a `hidden beast` number, since 2 + 21 + 643 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-221643 is a prime.

It is a Duffinian number.

221643 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4078 + ... + 4131.

It is an arithmetic number, because the mean of its divisors is an integer number (41050).

2²²¹⁶⁴³ is an apocalyptic number.

221643 is a deficient number, since it is larger than the sum of its proper divisors (106757).

221643 is an equidigital number, since it uses as much as digits as its factorization.

221643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8218 (or 8212 counting only the distinct ones).

The product of its digits is 288, while the sum is 18.

The square root of 221643 is about 470.7897619957. The cubic root of 221643 is about 60.5180148069.

Adding to 221643 its reverse (346122), we get a palindrome (567765).

The spelling of 221643 in words is "two hundred twenty-one thousand, six hundred forty-three".