21227765561 has 16 divisors (see below), whose sum is σ = 23073523200. Its totient is φ = 19455292800.

The previous prime is 21227765527. The next prime is 21227765563. The reversal of 21227765561 is 16556772212.

It is a cyclic number.

It is not a de Polignac number, because 21227765561 - 2¹⁴ = 21227749177 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21227765563) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3319355 + ... + 3325743.

It is an arithmetic number, because the mean of its divisors is an integer number (1442095200).

Almost surely, 2^21227765561 is an apocalyptic number.

It is an amenable number.

21227765561 is a deficient number, since it is larger than the sum of its proper divisors (1845757639).

21227765561 is a wasteful number, since it uses less digits than its factorization.

21227765561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12080.

The product of its digits is 352800, while the sum is 44.

The spelling of 21227765561 in words is "twenty-one billion, two hundred twenty-seven million, seven hundred sixty-five thousand, five hundred sixty-one".