21043331 has 4 divisors (see below), whose sum is σ = 22281192. Its totient is φ = 19805472.

The previous prime is 21043313. The next prime is 21043339. The reversal of 21043331 is 13334012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21043331 is a prime.

It is a super-2 number, since 2×21043331² = 885643559151122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (17), and also a Moran number because the ratio is a prime number: 1237843 = 21043331 / (2 + 1 + 0 + 4 + 3 + 3 + 3 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21043339) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 618905 + ... + 618938.

It is an arithmetic number, because the mean of its divisors is an integer number (5570298).

Almost surely, 2^21043331 is an apocalyptic number.

21043331 is a deficient number, since it is larger than the sum of its proper divisors (1237861).

21043331 is a wasteful number, since it uses less digits than its factorization.

21043331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1237860.

The product of its (nonzero) digits is 216, while the sum is 17.

The square root of 21043331 is about 4587.3010583566. The cubic root of 21043331 is about 276.0820443270.

Adding to 21043331 its reverse (13334012), we get a palindrome (34377343).

The spelling of 21043331 in words is "twenty-one million, forty-three thousand, three hundred thirty-one".