16561999998 has 96 divisors (see below), whose sum is σ = 39099220992. Its totient is φ = 5046912000.

The previous prime is 16561999997. The next prime is 16562000033. The reversal of 16561999998 is 89999916561.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561999997) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1632963 + ... + 1643073.

It is an arithmetic number, because the mean of its divisors is an integer number (407283552).

Almost surely, 2^16561999998 is an apocalyptic number.

16561999998 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 16561999998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (19549610496).

16561999998 is an abundant number, since it is smaller than the sum of its proper divisors (22537220994).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

16561999998 is a wasteful number, since it uses less digits than its factorization.

16561999998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10290 (or 10287 counting only the distinct ones).

The product of its digits is 85030560, while the sum is 72.

The spelling of 16561999998 in words is "sixteen billion, five hundred sixty-one million, nine hundred ninety-nine thousand, nine hundred ninety-eight".