221806 has 16 divisors (see below), whose sum is σ = 378000. Its totient is φ = 96768.

The previous prime is 221797. The next prime is 221807. The reversal of 221806 is 608122.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221807) by changing a digit.

221806 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 7 ways as a sum of consecutive naturals, for example, 270 + ... + 718.

It is an arithmetic number, because the mean of its divisors is an integer number (23625).

2²²¹⁸⁰⁶ is an apocalyptic number.

221806 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

221806 is a deficient number, since it is larger than the sum of its proper divisors (156194).

221806 is a wasteful number, since it uses less digits than its factorization.

221806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 483.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 221806 is about 470.9628435450. The cubic root of 221806 is about 60.5328464946.

Adding to 221806 its reverse (608122), we get a palindrome (829928).

The spelling of 221806 in words is "two hundred twenty-one thousand, eight hundred six".