21212442 has 28 divisors (see below), whose sum is σ = 47709450. Its totient is φ = 7070328.

The previous prime is 21212431. The next prime is 21212449. The reversal of 21212442 is 24421212.

21212442 is a `hidden beast` number, since 212 + 12 + 442 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14907321 + 6305121 = 3861^2 + 2511^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21212449) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 5817 + ... + 8732.

It is a self-describing number.

Almost surely, 2^21212442 is an apocalyptic number.

21212442 is an abundant number, since it is smaller than the sum of its proper divisors (26497008).

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

21212442 is an equidigital number, since it uses as much as digits as its factorization.

21212442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14569 (or 14554 counting only the distinct ones).

The product of its digits is 256, while the sum is 18.

The square root of 21212442 is about 4605.6966899699. The cubic root of 21212442 is about 276.8196334793.

Adding to 21212442 its reverse (24421212), we get a palindrome (45633654).

The spelling of 21212442 in words is "twenty-one million, two hundred twelve thousand, four hundred forty-two".