9975 has 24 divisors (see below), whose sum is σ = 19840. Its totient is φ = 4320.

The previous prime is 9973. The next prime is 10007. The reversal of 9975 is 5799.

It is a happy number.

It is not a de Polignac number, because 9975 - 2¹ = 9973 is a prime.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

It is a plaindrome in base 8.

It is a nialpdrome in base 10.

It is a congruent number.

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 23 ways as a sum of consecutive naturals, for example, 516 + ... + 534.

2⁹⁹⁷⁵ is an apocalyptic number.

9975 is a gapful number since it is divisible by the number (95) formed by its first and last digit.

9975 is a deficient number, since it is larger than the sum of its proper divisors (9865).

9975 is a wasteful number, since it uses less digits than its factorization.

9975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39 (or 34 counting only the distinct ones).

The product of its digits is 2835, while the sum is 30.

The square root of 9975 is about 99.8749217772. The cubic root of 9975 is about 21.5263782957.

Subtracting from 9975 its product of digits (2835), we obtain a triangular number (7140 = T₁₁₉).

The spelling of 9975 in words is "nine thousand, nine hundred seventy-five".