16661671538 has 4 divisors (see below), whose sum is σ = 24992507310. Its totient is φ = 8330835768.

The previous prime is 16661671531. The next prime is 16661671541. The reversal of 16661671538 is 83517616661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 83517616661 = 101149 ⋅825689.

It can be written as a sum of positive squares in only one way, i.e., 16303969969 + 357701569 = 127687^2 + 18913^2 .

It is a super-2 number, since 2×16661671538² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (16661671531) 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 as a sum of consecutive naturals, namely, 4165417883 + ... + 4165417886.

Almost surely, 2^16661671538 is an apocalyptic number.

16661671538 is a deficient number, since it is larger than the sum of its proper divisors (8330835772).

16661671538 is an equidigital number, since it uses as much as digits as its factorization.

16661671538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8330835771.

The product of its digits is 1088640, while the sum is 50.

The spelling of 16661671538 in words is "sixteen billion, six hundred sixty-one million, six hundred seventy-one thousand, five hundred thirty-eight".