21001012243 has 2 divisors, whose sum is σ = 21001012244. Its totient is φ = 21001012242.

The previous prime is 21001012199. The next prime is 21001012261. The reversal of 21001012243 is 34221010012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001012243 is a prime.

It is not a weakly prime, because it can be changed into another prime (21001012843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500506121 + 10500506122.

It is an arithmetic number, because the mean of its divisors is an integer number (10500506122).

Almost surely, 2^21001012243 is an apocalyptic number.

21001012243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001012243 is an equidigital number, since it uses as much as digits as its factorization.

21001012243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 16.

Adding to 21001012243 its reverse (34221010012), we get a palindrome (55222022255).

The spelling of 21001012243 in words is "twenty-one billion, one million, twelve thousand, two hundred forty-three".