15997985549 has 12 divisors (see below), whose sum is σ = 20041433244. Its totient is φ = 12657746304.

The previous prime is 15997985491. The next prime is 15997985557. The reversal of 15997985549 is 94558979951.

It can be written as a sum of positive squares in 2 ways, for example, as 8668913449 + 7329072100 = 93107^2 + 85610^2 .

It is not a de Polignac number, because 15997985549 - 2²⁰ = 15996936973 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15997985249) 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 11 ways as a sum of consecutive naturals, for example, 12556652 + ... + 12557925.

It is an arithmetic number, because the mean of its divisors is an integer number (1670119437).

Almost surely, 2^15997985549 is an apocalyptic number.

It is an amenable number.

15997985549 is a deficient number, since it is larger than the sum of its proper divisors (4043447695).

15997985549 is a wasteful number, since it uses less digits than its factorization.

15997985549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25114604 (or 25114597 counting only the distinct ones).

The product of its digits is 183708000, while the sum is 71.

The spelling of 15997985549 in words is "fifteen billion, nine hundred ninety-seven million, nine hundred eighty-five thousand, five hundred forty-nine".