9901 has 2 divisors, whose sum is σ = 9902. Its totient is φ = 9900.

The previous prime is 9887. The next prime is 9907. The reversal of 9901 is 1099.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9801 + 100 = 99^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 9901 - 2¹¹ = 7853 is a prime.

It is a Chen prime.

It is the 100-th Hogben number.

It is a plaindrome in base 13 and base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9907) by changing a digit.

It is a nontrivial repunit in base 99.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4950 + 4951.

It is an arithmetic number, because the mean of its divisors is an integer number (4951).

2⁹⁹⁰¹ is an apocalyptic number.

9901 is the 45-th centered decagonal number.

It is an amenable number.

9901 is a deficient number, since it is larger than the sum of its proper divisors (1).

9901 is an equidigital number, since it uses as much as digits as its factorization.

9901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81, while the sum is 19.

The square root of 9901 is about 99.5037687728. The cubic root of 9901 is about 21.4730146386.

The spelling of 9901 in words is "nine thousand, nine hundred one".