20121221161 has 2 divisors, whose sum is σ = 20121221162. Its totient is φ = 20121221160.

The previous prime is 20121221137. The next prime is 20121221249. The reversal of 20121221161 is 16112212102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14427613225 + 5693607936 = 120115^2 + 75456^2 .

It is a cyclic number.

It is not a de Polignac number, because 20121221161 - 2⁵ = 20121221129 is a prime.

It is not a weakly prime, because it can be changed into another prime (20121225161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10060610580 + 10060610581.

It is an arithmetic number, because the mean of its divisors is an integer number (10060610581).

Almost surely, 2^20121221161 is an apocalyptic number.

It is an amenable number.

20121221161 is a deficient number, since it is larger than the sum of its proper divisors (1).

20121221161 is an equidigital number, since it uses as much as digits as its factorization.

20121221161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 19.

Adding to 20121221161 its reverse (16112212102), we get a palindrome (36233433263).

The spelling of 20121221161 in words is "twenty billion, one hundred twenty-one million, two hundred twenty-one thousand, one hundred sixty-one".