21066436415509 has 2 divisors, whose sum is σ = 21066436415510. Its totient is φ = 21066436415508.

The previous prime is 21066436415483. The next prime is 21066436415539. The reversal of 21066436415509 is 90551463466012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15901512028900 + 5164924386609 = 3987670^2 + 2272647^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21066436415509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21066436415539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10533218207754 + 10533218207755.

It is an arithmetic number, because the mean of its divisors is an integer number (10533218207755).

Almost surely, 2^{21066436415509} is an apocalyptic number.

It is an amenable number.

21066436415509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21066436415509 is an equidigital number, since it uses as much as digits as its factorization.

21066436415509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4665600, while the sum is 52.

The spelling of 21066436415509 in words is "twenty-one trillion, sixty-six billion, four hundred thirty-six million, four hundred fifteen thousand, five hundred nine".