21840132 has 48 divisors (see below), whose sum is σ = 53343360. Its totient is φ = 6945792.

The previous prime is 21840131. The next prime is 21840149. The reversal of 21840132 is 23104812.

It is a junction number, because it is equal to n+sod(n) for n = 21840099 and 21840108.

It is not an unprimeable number, because it can be changed into a prime (21840131) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33433 + ... + 34079.

It is an arithmetic number, because the mean of its divisors is an integer number (1111320).

Almost surely, 2^21840132 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 21840132, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26671680).

21840132 is an abundant number, since it is smaller than the sum of its proper divisors (31503228).

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

21840132 is a wasteful number, since it uses less digits than its factorization.

21840132 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780 (or 778 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21840132 is about 4673.3427008941. The cubic root of 21840132 is about 279.5235605132.

Adding to 21840132 its reverse (23104812), we get a palindrome (44944944).

The spelling of 21840132 in words is "twenty-one million, eight hundred forty thousand, one hundred thirty-two".