21318344 has 8 divisors (see below), whose sum is σ = 39971910. Its totient is φ = 10659168.

The previous prime is 21318343. The next prime is 21318377. The reversal of 21318344 is 44381312.

It can be written as a sum of positive squares in only one way, i.e., 11142244 + 10176100 = 3338^2 + 3190^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21318343) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1332389 + ... + 1332404.

Almost surely, 2^21318344 is an apocalyptic number.

It is an amenable number.

21318344 is a deficient number, since it is larger than the sum of its proper divisors (18653566).

21318344 is a wasteful number, since it uses less digits than its factorization.

21318344 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2664799 (or 2664795 counting only the distinct ones).

The product of its digits is 2304, while the sum is 26.

The square root of 21318344 is about 4617.1792254579. The cubic root of 21318344 is about 277.2795381256.

Adding to 21318344 its reverse (44381312), we get a palindrome (65699656).

The spelling of 21318344 in words is "twenty-one million, three hundred eighteen thousand, three hundred forty-four".