21984638 has 16 divisors (see below), whose sum is σ = 37603440. Its totient is φ = 9549696.

The previous prime is 21984631. The next prime is 21984647. The reversal of 21984638 is 83648912.

It is a junction number, because it is equal to n+sod(n) for n = 21984595 and 21984604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21984631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24428 + ... + 25311.

It is an arithmetic number, because the mean of its divisors is an integer number (2350215).

Almost surely, 2^21984638 is an apocalyptic number.

21984638 is a deficient number, since it is larger than the sum of its proper divisors (15618802).

21984638 is a wasteful number, since it uses less digits than its factorization.

21984638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49771.

The product of its digits is 82944, while the sum is 41.

The square root of 21984638 is about 4688.7778791493. Note that the first 3 decimals coincide. The cubic root of 21984638 is about 280.1386982911.

It can be divided in two parts, 21984 and 638, that added together give a palindrome (22622).

The spelling of 21984638 in words is "twenty-one million, nine hundred eighty-four thousand, six hundred thirty-eight".