21831040 has 128 divisors (see below), whose sum is σ = 65214720. Its totient is φ = 6789120.

The previous prime is 21831023. The next prime is 21831041. The reversal of 21831040 is 4013812.

It is a tau number, because it is divible by the number of its divisors (128).

It is a junction number, because it is equal to n+sod(n) for n = 21830999 and 21831017.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21831041) 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, 49059 + ... + 49501.

It is an arithmetic number, because the mean of its divisors is an integer number (509490).

Almost surely, 2^21831040 is an apocalyptic number.

21831040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21831040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32607360).

21831040 is an abundant number, since it is smaller than the sum of its proper divisors (43383680).

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

21831040 is a wasteful number, since it uses less digits than its factorization.

21831040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480 (or 468 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21831040 is about 4672.3698483746. The cubic root of 21831040 is about 279.4847667770.

Adding to 21831040 its reverse (4013812), we get a palindrome (25844852).

It can be divided in two parts, 2183 and 1040, that added together give a palindrome (3223).

The spelling of 21831040 in words is "twenty-one million, eight hundred thirty-one thousand, forty".