21311019797 has 2 divisors, whose sum is σ = 21311019798. Its totient is φ = 21311019796.

The previous prime is 21311019767. The next prime is 21311019803. The reversal of 21311019797 is 79791011312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17086149796 + 4224870001 = 130714^2 + 64999^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311019797 - 2¹² = 21311015701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21311019757) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655509898 + 10655509899.

It is an arithmetic number, because the mean of its divisors is an integer number (10655509899).

Almost surely, 2^21311019797 is an apocalyptic number.

It is an amenable number.

21311019797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311019797 is an equidigital number, since it uses as much as digits as its factorization.

21311019797 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23814, while the sum is 41.

The spelling of 21311019797 in words is "twenty-one billion, three hundred eleven million, nineteen thousand, seven hundred ninety-seven".