21240644 has 24 divisors (see below), whose sum is σ = 39009600. Its totient is φ = 10105760.

The previous prime is 21240643. The next prime is 21240683. The reversal of 21240644 is 44604212.

It is not an unprimeable number, because it can be changed into a prime (21240643) 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, 6947 + ... + 9525.

It is an arithmetic number, because the mean of its divisors is an integer number (1625400).

Almost surely, 2^21240644 is an apocalyptic number.

It is an amenable number.

21240644 is a deficient number, since it is larger than the sum of its proper divisors (17768956).

21240644 is a wasteful number, since it uses less digits than its factorization.

21240644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2683 (or 2681 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 23.

The square root of 21240644 is about 4608.7573162405. The cubic root of 21240644 is about 276.9422566409.

Adding to 21240644 its reverse (44604212), we get a palindrome (65844856).

The spelling of 21240644 in words is "twenty-one million, two hundred forty thousand, six hundred forty-four".