16561373481 has 45 divisors (see below), whose sum is σ = 25196157063. Its totient is φ = 10840929840.

The previous prime is 16561373453. The next prime is 16561373483. The reversal of 16561373481 is 18437316561.

The square root of 16561373481 is 128691.

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

16561373481 is a `hidden beast` number, since 1 + 6 + 561 + 3 + 7 + 3 + 4 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 182493081 + 16378880400 = 13509^2 + 127980^2 .

It is not a de Polignac number, because 16561373481 - 2¹¹ = 16561371433 is a prime.

It is a super-2 number, since 2×16561373481² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (16561373483) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 91499211 + ... + 91499391.

Almost surely, 2^16561373481 is an apocalyptic number.

16561373481 is the 128691-st square number.

16561373481 is the 64346-th centered octagonal number.

It is an amenable number.

16561373481 is a deficient number, since it is larger than the sum of its proper divisors (8634783582).

16561373481 is an frugal number, since it uses more digits than its factorization.

16561373481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532 (or 263 counting only the distinct ones).

The product of its digits is 362880, while the sum is 45.

The spelling of 16561373481 in words is "sixteen billion, five hundred sixty-one million, three hundred seventy-three thousand, four hundred eighty-one".