2001 has 8 divisors (see below), whose sum is σ = 2880. Its totient is φ = 1232.

The previous prime is 1999. The next prime is 2003. The reversal of 2001 is 1002.

Added to its reverse (1002) it gives a triangular number (3003 = T₇₇).

It is an interprime number because it is at equal distance from previous prime (1999) and next prime (2003).

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

It is a cyclic number.

It is not a de Polignac number, because 2001 - 2¹ = 1999 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (3).

It is a Curzon number.

2001 is a lucky number.

It is a plaindrome in base 7 and base 11.

It is not an unprimeable number, because it can be changed into a prime (2003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55 + ... + 83.

It is an arithmetic number, because the mean of its divisors is an integer number (360).

2²⁰⁰¹ is an apocalyptic number.

It is an amenable number.

2001 is a deficient number, since it is larger than the sum of its proper divisors (879).

2001 is a wasteful number, since it uses less digits than its factorization.

2001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55.

The product of its (nonzero) digits is 2, while the sum is 3.

The square root of 2001 is about 44.7325384927. The cubic root of 2001 is about 12.6013100175.

Adding to 2001 its reverse (1002), we get a palindrome (3003).

Subtracting from 2001 its reverse (1002), we obtain a palindrome (999).

Multiplying 2001 by its reverse (1002), we get a palindrome (2005002).

The spelling of 2001 in words is "two thousand, one", and thus it is an iban number.