21122221212 has 72 divisors (see below), whose sum is σ = 55745464320. Its totient is φ = 6730780320.

The previous prime is 21122221193. The next prime is 21122221249. The reversal of 21122221212 is 21212222112.

It is a happy number.

21122221212 is a `hidden beast` number, since 211 + 22 + 221 + 212 = 666.

It is a super-2 number, since 2×21122221212² (a number of 21 digits) contains 22 as substring.

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1682037 + ... + 1694547.

It is an arithmetic number, because the mean of its divisors is an integer number (774242560).

Almost surely, 2^21122221212 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21122221212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27872732160).

21122221212 is an abundant number, since it is smaller than the sum of its proper divisors (34623243108).

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

21122221212 is a wasteful number, since it uses less digits than its factorization.

21122221212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14583 (or 14578 counting only the distinct ones).

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

Adding to 21122221212 its reverse (21212222112), we get a palindrome (42334443324).

The spelling of 21122221212 in words is "twenty-one billion, one hundred twenty-two million, two hundred twenty-one thousand, two hundred twelve".