21043871 has 2 divisors, whose sum is σ = 21043872. Its totient is φ = 21043870.

The previous prime is 21043817. The next prime is 21043901. The reversal of 21043871 is 17834012.

Together with previous prime (21043817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21043871 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21043871.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21043171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521935 + 10521936.

It is an arithmetic number, because the mean of its divisors is an integer number (10521936).

Almost surely, 2^21043871 is an apocalyptic number.

21043871 is a deficient number, since it is larger than the sum of its proper divisors (1).

21043871 is an equidigital number, since it uses as much as digits as its factorization.

21043871 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21043871 is about 4587.3599161173. The cubic root of 21043871 is about 276.0844058515.

Adding to 21043871 its reverse (17834012), we get a palindrome (38877883).

The spelling of 21043871 in words is "twenty-one million, forty-three thousand, eight hundred seventy-one".