21821536 has 48 divisors (see below), whose sum is σ = 47900160. Its totient is φ = 9700480.

The previous prime is 21821533. The next prime is 21821539. The reversal of 21821536 is 63512812.

It is an interprime number because it is at equal distance from previous prime (21821533) and next prime (21821539).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821533) 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 7 ways as a sum of consecutive naturals, for example, 15885 + ... + 17203.

It is an arithmetic number, because the mean of its divisors is an integer number (997920).

Almost surely, 2^21821536 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21821536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23950080).

21821536 is an abundant number, since it is smaller than the sum of its proper divisors (26078624).

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

21821536 is a wasteful number, since it uses less digits than its factorization.

21821536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1387 (or 1379 counting only the distinct ones).

The product of its digits is 2880, while the sum is 28.

The square root of 21821536 is about 4671.3526948840. The cubic root of 21821536 is about 279.4442036037. Note that the first 3 decimals are identical.

The spelling of 21821536 in words is "twenty-one million, eight hundred twenty-one thousand, five hundred thirty-six".