21115967216797 has 2 divisors, whose sum is σ = 21115967216798. Its totient is φ = 21115967216796.

The previous prime is 21115967216789. The next prime is 21115967216821. The reversal of 21115967216797 is 79761276951112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16202323594521 + 4913643622276 = 4025211^2 + 2216674^2 .

It is a cyclic number.

It is not a de Polignac number, because 21115967216797 - 2³ = 21115967216789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21115967316797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557983608398 + 10557983608399.

It is an arithmetic number, because the mean of its divisors is an integer number (10557983608399).

Almost surely, 2^{21115967216797} is an apocalyptic number.

It is an amenable number.

21115967216797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115967216797 is an equidigital number, since it uses as much as digits as its factorization.

21115967216797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20003760, while the sum is 64.

The spelling of 21115967216797 in words is "twenty-one trillion, one hundred fifteen billion, nine hundred sixty-seven million, two hundred sixteen thousand, seven hundred ninety-seven".