21010066561 has 16 divisors (see below), whose sum is σ = 23492564928. Its totient is φ = 18628632000.

The previous prime is 21010066559. The next prime is 21010066579. The reversal of 21010066561 is 16566001012.

It is not a de Polignac number, because 21010066561 - 2¹ = 21010066559 is a prime.

It is a super-3 number, since 3×21010066561³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21010066261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 66690 + ... + 215563.

It is an arithmetic number, because the mean of its divisors is an integer number (1468285308).

Almost surely, 2^21010066561 is an apocalyptic number.

It is an amenable number.

21010066561 is a deficient number, since it is larger than the sum of its proper divisors (2482498367).

21010066561 is a wasteful number, since it uses less digits than its factorization.

21010066561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 282432.

The product of its (nonzero) digits is 2160, while the sum is 28.

Adding to 21010066561 its reverse (16566001012), we get a palindrome (37576067573).

The spelling of 21010066561 in words is "twenty-one billion, ten million, sixty-six thousand, five hundred sixty-one".