21233540 has 12 divisors (see below), whose sum is σ = 44590476. Its totient is φ = 8493408.

The previous prime is 21233503. The next prime is 21233579. The reversal of 21233540 is 4533212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5345344 + 15888196 = 2312^2 + 3986^2 .

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1061677 = 21233540 / (2 + 1 + 2 + 3 + 3 + 5 + 4 + 0).

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, 530819 + ... + 530858.

It is an arithmetic number, because the mean of its divisors is an integer number (3715873).

Almost surely, 2^21233540 is an apocalyptic number.

21233540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21233540 is an abundant number, since it is smaller than the sum of its proper divisors (23356936).

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

21233540 is a wasteful number, since it uses less digits than its factorization.

21233540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1061686 (or 1061684 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 21233540 is about 4607.9865451192. The cubic root of 21233540 is about 276.9113784628.

Adding to 21233540 its reverse (4533212), we get a palindrome (25766752).

The spelling of 21233540 in words is "twenty-one million, two hundred thirty-three thousand, five hundred forty".