9978 has 8 divisors (see below), whose sum is σ = 19968. Its totient is φ = 3324.

The previous prime is 9973. The next prime is 10007. The reversal of 9978 is 8799.

9978 is nontrivially palindromic in base 5.

It is a sphenic number, since it is the product of 3 distinct primes.

9978 is an admirable number.

It is a nialpdrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (9973) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 826 + ... + 837.

It is an arithmetic number, because the mean of its divisors is an integer number (2496).

2⁹⁹⁷⁸ is an apocalyptic number.

9978 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (9984).

9978 is a wasteful number, since it uses less digits than its factorization.

9978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1668.

The product of its digits is 4536, while the sum is 33.

The square root of 9978 is about 99.8899394334. The cubic root of 9978 is about 21.5285361123.

Adding to 9978 its sum of digits (33), we get a triangular number (10011 = T₁₄₁).

The spelling of 9978 in words is "nine thousand, nine hundred seventy-eight".