21265944197 has 2 divisors, whose sum is σ = 21265944198. Its totient is φ = 21265944196.

The previous prime is 21265944173. The next prime is 21265944223. The reversal of 21265944197 is 79144956212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20382130756 + 883813441 = 142766^2 + 29729^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21265944197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21265934197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10632972098 + 10632972099.

It is an arithmetic number, because the mean of its divisors is an integer number (10632972099).

Almost surely, 2^21265944197 is an apocalyptic number.

It is an amenable number.

21265944197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21265944197 is an equidigital number, since it uses as much as digits as its factorization.

21265944197 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1088640, while the sum is 50.

The spelling of 21265944197 in words is "twenty-one billion, two hundred sixty-five million, nine hundred forty-four thousand, one hundred ninety-seven".