21421212 has 12 divisors (see below), whose sum is σ = 49982856. Its totient is φ = 7140400.

The previous prime is 21421201. The next prime is 21421243. The reversal of 21421212 is 21212412.

It is a tau number, because it is divible by the number of its divisors (12).

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 = 21421191 and 21421200.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 892539 + ... + 892562.

It is an arithmetic number, because the mean of its divisors is an integer number (4165238).

Almost surely, 2^21421212 is an apocalyptic number.

It is an amenable number.

21421212 is an abundant number, since it is smaller than the sum of its proper divisors (28561644).

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

21421212 is a wasteful number, since it uses less digits than its factorization.

21421212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1785108 (or 1785106 counting only the distinct ones).

The product of its digits is 64, while the sum is 15.

The square root of 21421212 is about 4628.3055214625. The cubic root of 21421212 is about 277.7248109261.

Adding to 21421212 its reverse (21212412), we get a palindrome (42633624).

The spelling of 21421212 in words is "twenty-one million, four hundred twenty-one thousand, two hundred twelve".