21806765573 has 2 divisors, whose sum is σ = 21806765574. Its totient is φ = 21806765572.

The previous prime is 21806765531. The next prime is 21806765593. The reversal of 21806765573 is 37556760812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19802681284 + 2004084289 = 140722^2 + 44767^2 .

It is a cyclic number.

It is not a de Polignac number, because 21806765573 - 2¹² = 21806761477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21806765503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10903382786 + 10903382787.

It is an arithmetic number, because the mean of its divisors is an integer number (10903382787).

Almost surely, 2^21806765573 is an apocalyptic number.

It is an amenable number.

21806765573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21806765573 is an equidigital number, since it uses as much as digits as its factorization.

21806765573 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2116800, while the sum is 50.

The spelling of 21806765573 in words is "twenty-one billion, eight hundred six million, seven hundred sixty-five thousand, five hundred seventy-three".