21317120 has 80 divisors (see below), whose sum is σ = 55831248. Its totient is φ = 7741440.

The previous prime is 21317083. The next prime is 21317129. The reversal of 21317120 is 2171312.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21317129) by changing a digit.

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, 27782 + ... + 28538.

Almost surely, 2^21317120 is an apocalyptic number.

21317120 is a gapful number since it is divisible by the number (20) 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 21317120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27915624).

21317120 is an abundant number, since it is smaller than the sum of its proper divisors (34514128).

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

21317120 is an equidigital number, since it uses as much as digits as its factorization.

21317120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 791 (or 775 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21317120 is about 4617.0466750944. The cubic root of 21317120 is about 277.2742313242.

Adding to 21317120 its reverse (2171312), we get a palindrome (23488432).

The spelling of 21317120 in words is "twenty-one million, three hundred seventeen thousand, one hundred twenty".