21330540 has 336 divisors, whose sum is σ = 88139520. Its totient is φ = 4199040.

The previous prime is 21330503. The next prime is 21330581. The reversal of 21330540 is 4503312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 1122651 + ... + 1122669.

It is an arithmetic number, because the mean of its divisors is an integer number (262320).

Almost surely, 2^21330540 is an apocalyptic number.

21330540 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 21330540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44069760).

21330540 is an abundant number, since it is smaller than the sum of its proper divisors (66808980).

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

21330540 is a wasteful number, since it uses less digits than its factorization.

21330540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64 (or 47 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21330540 is about 4618.4997564144. The cubic root of 21330540 is about 277.3324042796.

21330540 divided by its sum of digits (18) gives a triangular number (1185030 = T₁₅₃₉).

Adding to 21330540 its reverse (4503312), we get a palindrome (25833852).

The spelling of 21330540 in words is "twenty-one million, three hundred thirty thousand, five hundred forty".