21212144 has 20 divisors (see below), whose sum is σ = 41596296. Its totient is φ = 10477632.

The previous prime is 21212143. The next prime is 21212159. The reversal of 21212144 is 44121212.

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 (21212143) by changing a digit.

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, 6659 + ... + 9314.

Almost surely, 2^21212144 is an apocalyptic number.

It is an amenable number.

21212144 is a deficient number, since it is larger than the sum of its proper divisors (20384152).

21212144 is a wasteful number, since it uses less digits than its factorization.

21212144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16064 (or 16058 counting only the distinct ones).

The product of its digits is 128, while the sum is 17.

The square root of 21212144 is about 4605.6643386161. The cubic root of 21212144 is about 276.8183371861.

Adding to 21212144 its reverse (44121212), we get a palindrome (65333356).

The spelling of 21212144 in words is "twenty-one million, two hundred twelve thousand, one hundred forty-four".