21318320 has 20 divisors (see below), whose sum is σ = 49565280. Its totient is φ = 8527296.

The previous prime is 21318317. The next prime is 21318337. The reversal of 21318320 is 2381312.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21318292 and 21318301.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133160 + ... + 133319.

It is an arithmetic number, because the mean of its divisors is an integer number (2478264).

Almost surely, 2^21318320 is an apocalyptic number.

21318320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21318320 is an abundant number, since it is smaller than the sum of its proper divisors (28246960).

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

21318320 is a wasteful number, since it uses less digits than its factorization.

21318320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 266492 (or 266486 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21318320 is about 4617.1766264677. The cubic root of 21318320 is about 277.2794340726.

Adding to 21318320 its reverse (2381312), we get a palindrome (23699632).

The spelling of 21318320 in words is "twenty-one million, three hundred eighteen thousand, three hundred twenty".