20001661121 has 4 divisors (see below), whose sum is σ = 21540250452. Its totient is φ = 18463071792.

The previous prime is 20001661111. The next prime is 20001661123. The reversal of 20001661121 is 12116610002.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10263918721 + 9737742400 = 101311^2 + 98680^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20001661121 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20001661093 and 20001661102.

It is not an unprimeable number, because it can be changed into a prime (20001661123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 769294646 + ... + 769294671.

It is an arithmetic number, because the mean of its divisors is an integer number (5385062613).

Almost surely, 2^20001661121 is an apocalyptic number.

It is an amenable number.

20001661121 is a deficient number, since it is larger than the sum of its proper divisors (1538589331).

20001661121 is a wasteful number, since it uses less digits than its factorization.

20001661121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1538589330.

The product of its (nonzero) digits is 144, while the sum is 20.

The spelling of 20001661121 in words is "twenty billion, one million, six hundred sixty-one thousand, one hundred twenty-one".