21544638 has 8 divisors (see below), whose sum is σ = 43089288. Its totient is φ = 7181544.

The previous prime is 21544631. The next prime is 21544669. The reversal of 21544638 is 83644512.

It is a sphenic number, since it is the product of 3 distinct primes.

21544638 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21544599 and 21544608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21544631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1795381 + ... + 1795392.

It is an arithmetic number, because the mean of its divisors is an integer number (5386161).

Almost surely, 2^21544638 is an apocalyptic number.

21544638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21544638 is a wasteful number, since it uses less digits than its factorization.

21544638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3590778.

The product of its digits is 23040, while the sum is 33.

The square root of 21544638 is about 4641.6201912694. The cubic root of 21544638 is about 278.2571934474.

The spelling of 21544638 in words is "twenty-one million, five hundred forty-four thousand, six hundred thirty-eight".