20201221161 has 81 divisors (see below), whose sum is σ = 33079267767. Its totient is φ = 11870781120.

The previous prime is 20201221093. The next prime is 20201221171. The reversal of 20201221161 is 16112210202.

The square root of 20201221161 is 142131.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 11467197225 + 8734023936 = 107085^2 + 93456^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20201221161 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20201221171) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 276729021 + ... + 276729093.

Almost surely, 2^20201221161 is an apocalyptic number.

20201221161 is the 142131-st square number.

20201221161 is the 71066-th centered octagonal number.

It is an amenable number.

20201221161 is a deficient number, since it is larger than the sum of its proper divisors (12878046606).

20201221161 is an equidigital number, since it uses as much as digits as its factorization.

20201221161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 292 (or 146 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

Adding to 20201221161 its reverse (16112210202), we get a palindrome (36313431363).

The spelling of 20201221161 in words is "twenty billion, two hundred one million, two hundred twenty-one thousand, one hundred sixty-one".