15959521561 has 27 divisors (see below), whose sum is σ = 17282904093. Its totient is φ = 14735247840.

The previous prime is 15959521553. The next prime is 15959521603. The reversal of 15959521561 is 16512595951.

The square root of 15959521561 is 126331.

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

It can be written as a sum of positive squares in 4 ways, for example, as 2438483161 + 13521038400 = 49381^2 + 116280^2 .

It is not a de Polignac number, because 15959521561 - 2³ = 15959521553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15959521531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 146417575 + ... + 146417683.

It is an arithmetic number, because the mean of its divisors is an integer number (640107559).

Almost surely, 2^15959521561 is an apocalyptic number.

15959521561 is the 126331-st square number.

15959521561 is the 63166-th centered octagonal number.

It is an amenable number.

15959521561 is a deficient number, since it is larger than the sum of its proper divisors (1323382532).

15959521561 is an frugal number, since it uses more digits than its factorization.

15959521561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 378 (or 189 counting only the distinct ones).

The product of its digits is 607500, while the sum is 49.

Multiplying 15959521561 by its sum of digits (49), we get a square (782016556489 = 884317²).

The spelling of 15959521561 in words is "fifteen billion, nine hundred fifty-nine million, five hundred twenty-one thousand, five hundred sixty-one".