21233440 has 24 divisors (see below), whose sum is σ = 50164380. Its totient is φ = 8493312.

The previous prime is 21233413. The next prime is 21233441. The reversal of 21233440 is 4433212.

It can be written as a sum of positive squares in 2 ways, for example, as 21123216 + 110224 = 4596^2 + 332^2 .

It is not an unprimeable number, because it can be changed into a prime (21233441) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 66195 + ... + 66514.

Almost surely, 2^21233440 is an apocalyptic number.

21233440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21233440 is an abundant number, since it is smaller than the sum of its proper divisors (28930940).

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

21233440 is a wasteful number, since it uses less digits than its factorization.

21233440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132724 (or 132716 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 21233440 is about 4607.9756943803. The cubic root of 21233440 is about 276.9109437546.

Adding to 21233440 its reverse (4433212), we get a palindrome (25666652).

The spelling of 21233440 in words is "twenty-one million, two hundred thirty-three thousand, four hundred forty".