21244240 has 40 divisors (see below), whose sum is σ = 51101640. Its totient is φ = 8203776.

The previous prime is 21244231. The next prime is 21244243. The reversal of 21244240 is 4244212.

It can be written as a sum of positive squares in 4 ways, for example, as 341056 + 20903184 = 584^2 + 4572^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21244243) 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, 2259 + ... + 6898.

It is an arithmetic number, because the mean of its divisors is an integer number (1277541).

Almost surely, 2^21244240 is an apocalyptic number.

21244240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21244240 is an abundant number, since it is smaller than the sum of its proper divisors (29857400).

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

21244240 is a wasteful number, since it uses less digits than its factorization.

21244240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9199 (or 9193 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 19.

The square root of 21244240 is about 4609.1474265855. The cubic root of 21244240 is about 276.9578843554.

Adding to 21244240 its reverse (4244212), we get a palindrome (25488452).

The spelling of 21244240 in words is "twenty-one million, two hundred forty-four thousand, two hundred forty".