221212121220 has 144 divisors (see below), whose sum is σ = 695967068160. Its totient is φ = 56806541568.

The previous prime is 221212121177. The next prime is 221212121227. The reversal of 221212121220 is 22121212122.

It is a happy number.

221212121220 is a `hidden beast` number, since 221 + 212 + 1 + 212 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 221212121193 and 221212121202.

It is not an unprimeable number, because it can be changed into a prime (221212121227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1943937 + ... + 2054583.

It is an arithmetic number, because the mean of its divisors is an integer number (4833104640).

Almost surely, 2^221212121220 is an apocalyptic number.

221212121220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221212121220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (347983534080).

221212121220 is an abundant number, since it is smaller than the sum of its proper divisors (474754946940).

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

221212121220 is a wasteful number, since it uses less digits than its factorization.

221212121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111074 (or 111069 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 221212121220 its reverse (22121212122), we get a palindrome (243333333342).

The spelling of 221212121220 in words is "two hundred twenty-one billion, two hundred twelve million, one hundred twenty-one thousand, two hundred twenty".