21133890 has 96 divisors (see below), whose sum is σ = 61326720. Its totient is φ = 5018112.

The previous prime is 21133867. The next prime is 21133897. The reversal of 21133890 is 9833112.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21133897) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 28707 + ... + 29433.

It is an arithmetic number, because the mean of its divisors is an integer number (638820).

Almost surely, 2^21133890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21133890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30663360).

21133890 is an abundant number, since it is smaller than the sum of its proper divisors (40192830).

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

21133890 is a wasteful number, since it uses less digits than its factorization.

21133890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 776 (or 773 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21133890 is about 4597.1610804930. The cubic root of 21133890 is about 276.4775130035.

The spelling of 21133890 in words is "twenty-one million, one hundred thirty-three thousand, eight hundred ninety".