21123299967509 has 2 divisors, whose sum is σ = 21123299967510. Its totient is φ = 21123299967508.

The previous prime is 21123299967467. The next prime is 21123299967577. The reversal of 21123299967509 is 90576999232112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17874690255409 + 3248609712100 = 4227847^2 + 1802390^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123299967509 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123299961509) 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, 10561649983754 + 10561649983755.

It is an arithmetic number, because the mean of its divisors is an integer number (10561649983755).

Almost surely, 2^{21123299967509} is an apocalyptic number.

It is an amenable number.

21123299967509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123299967509 is an equidigital number, since it uses as much as digits as its factorization.

21123299967509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 33067440, while the sum is 65.

The spelling of 21123299967509 in words is "twenty-one trillion, one hundred twenty-three billion, two hundred ninety-nine million, nine hundred sixty-seven thousand, five hundred nine".