21643344 has 30 divisors (see below), whose sum is σ = 60571706. Its totient is φ = 7214400.

The previous prime is 21643333. The next prime is 21643351. The reversal of 21643344 is 44334612.

It can be written as a sum of positive squares in only one way, i.e., 14288400 + 7354944 = 3780^2 + 2712^2 .

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 75007 + ... + 75294.

Almost surely, 2^21643344 is an apocalyptic number.

21643344 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21643344 is an abundant number, since it is smaller than the sum of its proper divisors (38928362).

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

21643344 is a wasteful number, since it uses less digits than its factorization.

21643344 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150315 (or 150306 counting only the distinct ones).

The product of its digits is 6912, while the sum is 27.

The square root of 21643344 is about 4652.2407504341. The cubic root of 21643344 is about 278.6814879851.

Adding to 21643344 its reverse (44334612), we get a palindrome (65977956).

The spelling of 21643344 in words is "twenty-one million, six hundred forty-three thousand, three hundred forty-four".