21303440 has 20 divisors (see below), whose sum is σ = 49530684. Its totient is φ = 8521344.

The previous prime is 21303421. The next prime is 21303467. The reversal of 21303440 is 4430312.

It can be written as a sum of positive squares in 2 ways, for example, as 4787344 + 16516096 = 2188^2 + 4064^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133067 + ... + 133226.

Almost surely, 2^21303440 is an apocalyptic number.

21303440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21303440 is an abundant number, since it is smaller than the sum of its proper divisors (28227244).

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

21303440 is a wasteful number, since it uses less digits than its factorization.

21303440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266306 (or 266300 counting only the distinct ones).

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

The square root of 21303440 is about 4615.5649708351. The cubic root of 21303440 is about 277.2149061876.

Adding to 21303440 its reverse (4430312), we get a palindrome (25733752).

The spelling of 21303440 in words is "twenty-one million, three hundred three thousand, four hundred forty".