21817144 has 8 divisors (see below), whose sum is σ = 40907160. Its totient is φ = 10908568.

The previous prime is 21817141. The next prime is 21817153. The reversal of 21817144 is 44171812.

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21817141) 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 as a sum of consecutive naturals, namely, 1363564 + ... + 1363579.

It is an arithmetic number, because the mean of its divisors is an integer number (5113395).

Almost surely, 2^21817144 is an apocalyptic number.

It is an amenable number.

21817144 is a deficient number, since it is larger than the sum of its proper divisors (19090016).

21817144 is a wasteful number, since it uses less digits than its factorization.

21817144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2727149 (or 2727145 counting only the distinct ones).

The product of its digits is 1792, while the sum is 28.

The square root of 21817144 is about 4670.8825718487. The cubic root of 21817144 is about 279.4254545219.

Adding to 21817144 its reverse (44171812), we get a palindrome (65988956).

The spelling of 21817144 in words is "twenty-one million, eight hundred seventeen thousand, one hundred forty-four".