16666961385361 has 27 divisors (see below), whose sum is σ = 19611382151601. Its totient is φ = 14123294849664.

The previous prime is 16666961385311. The next prime is 16666961385419. The reversal of 16666961385361 is 16358316966661.

The square root of 16666961385361 is 4082519.

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 3772082574225 + 12894878811136 = 1942185^2 + 3590944^2 .

It is not a de Polignac number, because 16666961385361 - 2¹¹ = 16666961383313 is a prime.

It is a super-3 number, since 3×16666961385361³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16666961385311) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 2543406061 + ... + 2543412613.

Almost surely, 2^{16666961385361} is an apocalyptic number.

16666961385361 is the 4082519-th square number.

16666961385361 is the 2041260-th centered octagonal number.

It is an amenable number.

16666961385361 is a deficient number, since it is larger than the sum of its proper divisors (2944420766240).

16666961385361 is an frugal number, since it uses more digits than its factorization.

16666961385361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13298 (or 6649 counting only the distinct ones).

The product of its digits is 151165440, while the sum is 67.

The spelling of 16666961385361 in words is "sixteen trillion, six hundred sixty-six billion, nine hundred sixty-one million, three hundred eighty-five thousand, three hundred sixty-one".