21104243 has 2 divisors, whose sum is σ = 21104244. Its totient is φ = 21104242.

The previous prime is 21104233. The next prime is 21104249. The reversal of 21104243 is 34240112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21104243 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21104249) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552121 + 10552122.

It is an arithmetic number, because the mean of its divisors is an integer number (10552122).

Almost surely, 2^21104243 is an apocalyptic number.

21104243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21104243 is an equidigital number, since it uses as much as digits as its factorization.

21104243 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21104243 is about 4593.9354588414. The cubic root of 21104243 is about 276.3481699648.

Adding to 21104243 its reverse (34240112), we get a palindrome (55344355).

The spelling of 21104243 in words is "twenty-one million, one hundred four thousand, two hundred forty-three".