989668721778 has 64 divisors (see below), whose sum is σ = 2273873057280. Its totient is φ = 283996713600.

The previous prime is 989668721773. The next prime is 989668721791. The reversal of 989668721778 is 877127866989.

989668721778 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (989668721773) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2859726 + ... + 3187062.

It is an arithmetic number, because the mean of its divisors is an integer number (35529266520).

Almost surely, 2^989668721778 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 989668721778, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1136936528640).

989668721778 is an abundant number, since it is smaller than the sum of its proper divisors (1284204335502).

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

989668721778 is a wasteful number, since it uses less digits than its factorization.

989668721778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329783.

The product of its digits is 1024192512, while the sum is 78.

The spelling of 989668721778 in words is "nine hundred eighty-nine billion, six hundred sixty-eight million, seven hundred twenty-one thousand, seven hundred seventy-eight".