21221212 has 6 divisors (see below), whose sum is σ = 37137128. Its totient is φ = 10610604.

The previous prime is 21221171. The next prime is 21221237. The reversal of 21221212 is 21212212.

It is a happy number.

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

It is a junction number, because it is equal to n+sod(n) for n = 21221192 and 21221201.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2652648 + ... + 2652655.

Almost surely, 2^21221212 is an apocalyptic number.

It is an amenable number.

21221212 is a deficient number, since it is larger than the sum of its proper divisors (15915916).

21221212 is a wasteful number, since it uses less digits than its factorization.

21221212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5305307 (or 5305305 counting only the distinct ones).

The product of its digits is 32, while the sum is 13.

The square root of 21221212 is about 4606.6486733850. The cubic root of 21221212 is about 276.8577773463.

Adding to 21221212 its reverse (21212212), we get a palindrome (42433424).

It can be divided in two parts, 212 and 21212, that multiplied together give a palindrome (4496944).

The spelling of 21221212 in words is "twenty-one million, two hundred twenty-one thousand, two hundred twelve".