21443240 has 128 divisors (see below), whose sum is σ = 61205760. Its totient is φ = 6580224.

The previous prime is 21443221. The next prime is 21443263. The reversal of 21443240 is 4234412.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 156452 + ... + 156588.

It is an arithmetic number, because the mean of its divisors is an integer number (478170).

Almost surely, 2^21443240 is an apocalyptic number.

21443240 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 21443240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30602880).

21443240 is an abundant number, since it is smaller than the sum of its proper divisors (39762520).

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

21443240 is a wasteful number, since it uses less digits than its factorization.

21443240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211 (or 207 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 21443240 is about 4630.6846146115. The cubic root of 21443240 is about 277.8199755745.

Adding to 21443240 its reverse (4234412), we get a palindrome (25677652).

The spelling of 21443240 in words is "twenty-one million, four hundred forty-three thousand, two hundred forty".