21217344 has 56 divisors (see below), whose sum is σ = 57119520. Its totient is φ = 6948864.

The previous prime is 21217337. The next prime is 21217367. The reversal of 21217344 is 44371212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

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 7 ways as a sum of consecutive naturals, for example, 10392 + ... + 12264.

Almost surely, 2^21217344 is an apocalyptic number.

21217344 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21217344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28559760).

21217344 is an abundant number, since it is smaller than the sum of its proper divisors (35902176).

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

21217344 is a wasteful number, since it uses less digits than its factorization.

21217344 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1947 (or 1937 counting only the distinct ones).

The product of its digits is 1344, while the sum is 24.

The square root of 21217344 is about 4606.2288262743. The cubic root of 21217344 is about 276.8409553263.

Adding to 21217344 its reverse (44371212), we get a palindrome (65588556).

The spelling of 21217344 in words is "twenty-one million, two hundred seventeen thousand, three hundred forty-four".