21444444 has 72 divisors (see below), whose sum is σ = 63423360. Its totient is φ = 5981472.

The previous prime is 21444433. The next prime is 21444457. The reversal of 21444444 is 44444412.

21444444 is a `hidden beast` number, since 214 + 4 + 4 + 444 = 666.

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

21444444 is a modest number, since divided by 4444 gives 2144 as remainder.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9847 + ... + 11825.

It is an arithmetic number, because the mean of its divisors is an integer number (880880).

Almost surely, 2^21444444 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 21444444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31711680).

21444444 is an abundant number, since it is smaller than the sum of its proper divisors (41978916).

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

21444444 is a wasteful number, since it uses less digits than its factorization.

21444444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2039 (or 2034 counting only the distinct ones).

The product of its digits is 8192, while the sum is 27.

The square root of 21444444 is about 4630.8146151622. The cubic root of 21444444 is about 277.8251751773.

Adding to 21444444 its reverse (44444412), we get a palindrome (65888856).

The spelling of 21444444 in words is "twenty-one million, four hundred forty-four thousand, four hundred forty-four".