2001221001 has 12 divisors (see below), whose sum is σ = 3113010628. Its totient is φ = 1231520544.

The previous prime is 2001220987. The next prime is 2001221039. The reversal of 2001221001 is 1001221002.

It can be written as a sum of positive squares in 2 ways, for example, as 1230325776 + 770895225 = 35076^2 + 27765^2 .

It is not a de Polignac number, because 2001221001 - 2¹⁸ = 2000958857 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is not an unprimeable number, because it can be changed into a prime (2001221071) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8552110 + ... + 8552343.

Almost surely, 2^2001221001 is an apocalyptic number.

It is an amenable number.

2001221001 is a deficient number, since it is larger than the sum of its proper divisors (1111789627).

2001221001 is a wasteful number, since it uses less digits than its factorization.

2001221001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17104472 (or 17104469 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 2001221001 is about 44735.0086732975. The cubic root of 2001221001 is about 1260.1773918800.

Adding to 2001221001 its reverse (1001221002), we get a palindrome (3002442003).

Subtracting from 2001221001 its reverse (1001221002), we obtain a palindrome (999999999).

The spelling of 2001221001 in words is "two billion, one million, two hundred twenty-one thousand, one".