21559342561 has 9 divisors (see below), whose sum is σ = 21672552531. Its totient is φ = 21446723184.

The previous prime is 21559342547. The next prime is 21559342577. The reversal of 21559342561 is 16524395512.

The square root of 21559342561 is 146831.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 19703456161 + 1855886400 = 140369^2 + 43080^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21559342561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21559348561) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 52712125 + ... + 52712533.

Almost surely, 2^21559342561 is an apocalyptic number.

21559342561 is the 146831-st square number.

21559342561 is the 73416-th centered octagonal number.

It is an amenable number.

21559342561 is a deficient number, since it is larger than the sum of its proper divisors (113209970).

21559342561 is an frugal number, since it uses more digits than its factorization.

21559342561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1536 (or 768 counting only the distinct ones).

The product of its digits is 324000, while the sum is 43.

The spelling of 21559342561 in words is "twenty-one billion, five hundred fifty-nine million, three hundred forty-two thousand, five hundred sixty-one".