21043240 has 32 divisors (see below), whose sum is σ = 47628000. Its totient is φ = 8367424.

The previous prime is 21043237. The next prime is 21043259. The reversal of 21043240 is 4234012.

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 7 ways as a sum of consecutive naturals, for example, 5691 + ... + 8629.

It is an arithmetic number, because the mean of its divisors is an integer number (1488375).

Almost surely, 2^21043240 is an apocalyptic number.

21043240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21043240 is an abundant number, since it is smaller than the sum of its proper divisors (26584760).

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

21043240 is a wasteful number, since it uses less digits than its factorization.

21043240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3129 (or 3125 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21043240 is about 4587.2911396597. The cubic root of 21043240 is about 276.0816463624.

Adding to 21043240 its reverse (4234012), we get a palindrome (25277252).

The spelling of 21043240 in words is "twenty-one million, forty-three thousand, two hundred forty".