21004043 has 2 divisors, whose sum is σ = 21004044. Its totient is φ = 21004042.

The previous prime is 21003937. The next prime is 21004057. The reversal of 21004043 is 34040012.

It is an a-pointer prime, because the next prime (21004057) can be obtained adding 21004043 to its sum of digits (14).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21004043 - 2¹⁶ = 20938507 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21004073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502021 + 10502022.

It is an arithmetic number, because the mean of its divisors is an integer number (10502022).

Almost surely, 2^21004043 is an apocalyptic number.

21004043 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004043 is an equidigital number, since it uses as much as digits as its factorization.

21004043 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21004043 is about 4583.0168011911. The cubic root of 21004043 is about 275.9101217884.

Adding to 21004043 its reverse (34040012), we get a palindrome (55044055).

The spelling of 21004043 in words is "twenty-one million, four thousand, forty-three".