221812 has 12 divisors (see below), whose sum is σ = 405216. Its totient is φ = 106040.

The previous prime is 221807. The next prime is 221813. The reversal of 221812 is 218122.

221812 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is an Ulam number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221813) by changing a digit.

221812 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 3 ways as a sum of consecutive naturals, for example, 1114 + ... + 1297.

It is an arithmetic number, because the mean of its divisors is an integer number (33768).

2²²¹⁸¹² is an apocalyptic number.

It is an amenable number.

221812 is a deficient number, since it is larger than the sum of its proper divisors (183404).

221812 is a wasteful number, since it uses less digits than its factorization.

221812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2438 (or 2436 counting only the distinct ones).

The product of its digits is 64, while the sum is 16.

The square root of 221812 is about 470.9692134312. The cubic root of 221812 is about 60.5333923076.

Adding to 221812 its reverse (218122), we get a palindrome (439934).

The spelling of 221812 in words is "two hundred twenty-one thousand, eight hundred twelve".