21817152 has 126 divisors (see below), whose sum is σ = 72838818. Its totient is φ = 6225408.

The previous prime is 21817141. The next prime is 21817153. The reversal of 21817152 is 25171812.

It can be written as a sum of positive squares in only one way, i.e., 13660416 + 8156736 = 3696^2 + 2856^2 .

It is a tau number, because it is divible by the number of its divisors (126).

It is a super-2 number, since 2×21817152² = 951976242782208, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21817153) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 27838 + ... + 28610.

Almost surely, 2^21817152 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 21817152, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36419409).

21817152 is an abundant number, since it is smaller than the sum of its proper divisors (51021666).

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

21817152 is a wasteful number, since it uses less digits than its factorization.

21817152 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 805 (or 785 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 21817152 is about 4670.8834282178. The cubic root of 21817152 is about 279.4254886755.

Adding to 21817152 its reverse (25171812), we get a palindrome (46988964).

The spelling of 21817152 in words is "twenty-one million, eight hundred seventeen thousand, one hundred fifty-two".