21221212212 has 144 divisors (see below), whose sum is σ = 55959098832. Its totient is φ = 6775142400.

The previous prime is 21221212171. The next prime is 21221212213.

It is a happy number.

21221212212 is a `hidden beast` number, since 21 + 221 + 212 + 212 = 666.

21221212212 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in 8 ways, for example, as 9140124816 + 12081087396 = 95604^2 + 109914^2 .

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 not an unprimeable number, because it can be changed into a prime (21221212213) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 31345618 + ... + 31346294.

It is an arithmetic number, because the mean of its divisors is an integer number (388604853).

Almost surely, 2^21221212212 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 21221212212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27979549416).

21221212212 is an abundant number, since it is smaller than the sum of its proper divisors (34737886620).

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

21221212212 is a wasteful number, since it uses less digits than its factorization.

21221212212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1058 (or 1053 counting only the distinct ones).

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

The spelling of 21221212212 in words is "twenty-one billion, two hundred twenty-one million, two hundred twelve thousand, two hundred twelve".