2100001221 has 10 divisors (see below), whose sum is σ = 3137038982. Its totient is φ = 1400000760.

The previous prime is 2100001207. The next prime is 2100001231. The reversal of 2100001221 is 1221000012.

It can be written as a sum of positive squares in only one way, i.e., 1518660900 + 581340321 = 38970^2 + 24111^2 .

It is not a de Polignac number, because 2100001221 - 2¹³ = 2099993029 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2100001231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 12962890 + ... + 12963051.

Almost surely, 2^2100001221 is an apocalyptic number.

It is an amenable number.

2100001221 is a deficient number, since it is larger than the sum of its proper divisors (1037037761).

2100001221 is an equidigital number, since it uses as much as digits as its factorization.

2100001221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25925953 (or 25925944 counting only the distinct ones).

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

The square root of 2100001221 is about 45825.7702717587. The cubic root of 2100001221 is about 1280.5794131759.

Adding to 2100001221 its reverse (1221000012), we get a palindrome (3321001233).

The spelling of 2100001221 in words is "two billion, one hundred million, one thousand, two hundred twenty-one".