16561628209946 has 4 divisors (see below), whose sum is σ = 24842442314922. Its totient is φ = 8280814104972.

The previous prime is 16561628209909. The next prime is 16561628209949. The reversal of 16561628209946 is 64990282616561.

16561628209946 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.

It can be written as a sum of positive squares in only one way, i.e., 14385445624225 + 2176182585721 = 3792815^2 + 1475189^2 .

It is not an unprimeable number, because it can be changed into a prime (16561628209949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4140407052485 + ... + 4140407052488.

Almost surely, 2^{16561628209946} is an apocalyptic number.

16561628209946 is a deficient number, since it is larger than the sum of its proper divisors (8280814104976).

16561628209946 is an equidigital number, since it uses as much as digits as its factorization.

16561628209946 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8280814104975.

The product of its (nonzero) digits is 67184640, while the sum is 65.

The spelling of 16561628209946 in words is "sixteen trillion, five hundred sixty-one billion, six hundred twenty-eight million, two hundred nine thousand, nine hundred forty-six".