21790440 has 96 divisors (see below), whose sum is σ = 80945280. Its totient is φ = 4980096.

The previous prime is 21790429. The next prime is 21790441. The reversal of 21790440 is 4409712.

It is a happy number.

21790440 is a `hidden beast` number, since 217 + 9 + 0 + 440 = 666.

It is not an unprimeable number, because it can be changed into a prime (21790441) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1804 + ... + 6843.

It is an arithmetic number, because the mean of its divisors is an integer number (843180).

Almost surely, 2^21790440 is an apocalyptic number.

21790440 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 21790440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40472640).

21790440 is an abundant number, since it is smaller than the sum of its proper divisors (59154840).

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

21790440 is a wasteful number, since it uses less digits than its factorization.

21790440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8671 (or 8664 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21790440 is about 4668.0231361895. The cubic root of 21790440 is about 279.3114031778.

The spelling of 21790440 in words is "twenty-one million, seven hundred ninety thousand, four hundred forty".