21612640541209 has 2 divisors, whose sum is σ = 21612640541210. Its totient is φ = 21612640541208.

The previous prime is 21612640541131. The next prime is 21612640541269. The reversal of 21612640541209 is 90214504621612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15050830611600 + 6561809929609 = 3879540^2 + 2561603^2 .

It is a cyclic number.

It is not a de Polignac number, because 21612640541209 - 2²⁷ = 21612506323481 is a prime.

It is not a weakly prime, because it can be changed into another prime (21612640541269) 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, 10806320270604 + 10806320270605.

It is an arithmetic number, because the mean of its divisors is an integer number (10806320270605).

Almost surely, 2^{21612640541209} is an apocalyptic number.

It is an amenable number.

21612640541209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612640541209 is an equidigital number, since it uses as much as digits as its factorization.

21612640541209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 207360, while the sum is 43.

The spelling of 21612640541209 in words is "twenty-one trillion, six hundred twelve billion, six hundred forty million, five hundred forty-one thousand, two hundred nine".