221220121212 has 36 divisors (see below), whose sum is σ = 559441963080. Its totient is φ = 73707514272.

The previous prime is 221220121211. The next prime is 221220121223. The reversal of 221220121212 is 212121022122.

It is a happy number.

221220121212 is a `hidden beast` number, since 221 + 220 + 1 + 212 + 12 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221220121211) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1272438 + ... + 1435805.

It is an arithmetic number, because the mean of its divisors is an integer number (15540054530).

Almost surely, 2^221220121212 is an apocalyptic number.

It is an amenable number.

221220121212 is an abundant number, since it is smaller than the sum of its proper divisors (338221841868).

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

221220121212 is a wasteful number, since it uses less digits than its factorization.

221220121212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2710522 (or 2710517 counting only the distinct ones).

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

Adding to 221220121212 its reverse (212121022122), we get a palindrome (433341143334).

The spelling of 221220121212 in words is "two hundred twenty-one billion, two hundred twenty million, one hundred twenty-one thousand, two hundred twelve".