21318540 has 48 divisors (see below), whose sum is σ = 61087488. Its totient is φ = 5552064.

The previous prime is 21318533. The next prime is 21318541. The reversal of 21318540 is 4581312.

It is a self number, because there is not a number n which added to its sum of digits gives 21318540.

It is not an unprimeable number, because it can be changed into a prime (21318541) 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 15 ways as a sum of consecutive naturals, for example, 1552 + ... + 6711.

It is an arithmetic number, because the mean of its divisors is an integer number (1272656).

Almost surely, 2^21318540 is an apocalyptic number.

21318540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21318540 is an abundant number, since it is smaller than the sum of its proper divisors (39768948).

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

21318540 is a wasteful number, since it uses less digits than its factorization.

21318540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8318 (or 8316 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 21318540 is about 4617.2004504895. The cubic root of 21318540 is about 277.2803878886.

Adding to 21318540 its reverse (4581312), we get a palindrome (25899852).

The spelling of 21318540 in words is "twenty-one million, three hundred eighteen thousand, five hundred forty".