21518280 has 96 divisors (see below), whose sum is σ = 79934400. Its totient is φ = 4917888.

The previous prime is 21518269. The next prime is 21518281. The reversal of 21518280 is 8281512.

It is not an unprimeable number, because it can be changed into a prime (21518281) 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 23 ways as a sum of consecutive naturals, for example, 1750 + ... + 6789.

It is an arithmetic number, because the mean of its divisors is an integer number (832650).

Almost surely, 2^21518280 is an apocalyptic number.

21518280 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 21518280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39967200).

21518280 is an abundant number, since it is smaller than the sum of its proper divisors (58416120).

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

21518280 is a wasteful number, since it uses less digits than its factorization.

21518280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8563 (or 8556 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 21518280 is about 4638.7800120290. The cubic root of 21518280 is about 278.1436726091.

Adding to 21518280 its reverse (8281512), we get a palindrome (29799792).

The spelling of 21518280 in words is "twenty-one million, five hundred eighteen thousand, two hundred eighty".