21033440 has 48 divisors (see below), whose sum is σ = 50766912. Its totient is φ = 8231424.

The previous prime is 21033433. The next prime is 21033443. The reversal of 21033440 is 4433012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21033443) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6122 + ... + 8918.

It is an arithmetic number, because the mean of its divisors is an integer number (1057644).

Almost surely, 2^21033440 is an apocalyptic number.

21033440 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 21033440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25383456).

21033440 is an abundant number, since it is smaller than the sum of its proper divisors (29733472).

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

21033440 is a wasteful number, since it uses less digits than its factorization.

21033440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2859 (or 2851 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 17.

The square root of 21033440 is about 4586.2228467444. Note that the first 3 decimals coincide. The cubic root of 21033440 is about 276.0387819199.

Adding to 21033440 its reverse (4433012), we get a palindrome (25466452).

The spelling of 21033440 in words is "twenty-one million, thirty-three thousand, four hundred forty".