16861801609 has 3 divisors (see below), whose sum is σ = 16861931463. Its totient is φ = 16861671756.

The previous prime is 16861801601. The next prime is 16861801637. The reversal of 16861801609 is 90610816861.

It is a happy number.

The square root of 16861801609 is 129853.

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

16861801609 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 161925625 + 16699875984 = 12725^2 + 129228^2 .

It is not a de Polignac number, because 16861801609 - 2³ = 16861801601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16861801601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 64927 + ... + 194779.

It is an arithmetic number, because the mean of its divisors is an integer number (5620643821).

Almost surely, 2^16861801609 is an apocalyptic number.

16861801609 is the 129853-rd square number.

16861801609 is the 64927-th centered octagonal number.

It is an amenable number.

16861801609 is a deficient number, since it is larger than the sum of its proper divisors (129854).

16861801609 is an frugal number, since it uses more digits than its factorization.

16861801609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 259706 (or 129853 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 46.

The spelling of 16861801609 in words is "sixteen billion, eight hundred sixty-one million, eight hundred one thousand, six hundred nine".