21540244 has 12 divisors (see below), whose sum is σ = 41122368. Its totient is φ = 9791000.

The previous prime is 21540229. The next prime is 21540247. The reversal of 21540244 is 44204512.

It is a happy number.

It is a super-2 number, since 2×21540244² = 927964223159072, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540247) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 244732 + ... + 244819.

It is an arithmetic number, because the mean of its divisors is an integer number (3426864).

Almost surely, 2^21540244 is an apocalyptic number.

It is an amenable number.

21540244 is a deficient number, since it is larger than the sum of its proper divisors (19582124).

21540244 is a wasteful number, since it uses less digits than its factorization.

21540244 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 489566 (or 489564 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 22.

The square root of 21540244 is about 4641.1468410297. The cubic root of 21540244 is about 278.2382754342.

Adding to 21540244 its reverse (44204512), we get a palindrome (65744756).

The spelling of 21540244 in words is "twenty-one million, five hundred forty thousand, two hundred forty-four".