21636213165209 has 2 divisors, whose sum is σ = 21636213165210. Its totient is φ = 21636213165208.

The previous prime is 21636213165179. The next prime is 21636213165379. The reversal of 21636213165209 is 90256131263612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21112674091609 + 523539073600 = 4594853^2 + 723560^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21636213165209 is a prime.

It is not a weakly prime, because it can be changed into another prime (21636213135209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10818106582604 + 10818106582605.

It is an arithmetic number, because the mean of its divisors is an integer number (10818106582605).

Almost surely, 2^{21636213165209} is an apocalyptic number.

It is an amenable number.

21636213165209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21636213165209 is an equidigital number, since it uses as much as digits as its factorization.

21636213165209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 699840, while the sum is 47.

The spelling of 21636213165209 in words is "twenty-one trillion, six hundred thirty-six billion, two hundred thirteen million, one hundred sixty-five thousand, two hundred nine".