21133891 has 8 divisors (see below), whose sum is σ = 21441024. Its totient is φ = 20829000.

The previous prime is 21133867. The next prime is 21133897. The reversal of 21133891 is 19833112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21133891 - 2¹⁵ = 21101123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21133897) 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, 27766 + ... + 28516.

It is an arithmetic number, because the mean of its divisors is an integer number (2680128).

Almost surely, 2^21133891 is an apocalyptic number.

21133891 is the 2908-th centered pentagonal number.

21133891 is a deficient number, since it is larger than the sum of its proper divisors (307133).

21133891 is a wasteful number, since it uses less digits than its factorization.

21133891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1121.

The product of its digits is 1296, while the sum is 28.

The square root of 21133891 is about 4597.1611892558. The cubic root of 21133891 is about 276.4775173642.

The spelling of 21133891 in words is "twenty-one million, one hundred thirty-three thousand, eight hundred ninety-one".