20121221221 has 4 divisors (see below), whose sum is σ = 20178875500. Its totient is φ = 20063566944.

The previous prime is 20121221161. The next prime is 20121221249. The reversal of 20121221221 is 12212212102.

It is a happy number.

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 10926520900 + 9194700321 = 104530^2 + 95889^2 .

It is a cyclic number.

It is not a de Polignac number, because 20121221221 - 2¹³ = 20121213029 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20121221195 and 20121221204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20121221621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28826616 + ... + 28827313.

It is an arithmetic number, because the mean of its divisors is an integer number (5044718875).

Almost surely, 2^20121221221 is an apocalyptic number.

It is an amenable number.

20121221221 is a deficient number, since it is larger than the sum of its proper divisors (57654279).

20121221221 is an equidigital number, since it uses as much as digits as its factorization.

20121221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57654278.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 20121221221 its reverse (12212212102), we get a palindrome (32333433323).

The spelling of 20121221221 in words is "twenty billion, one hundred twenty-one million, two hundred twenty-one thousand, two hundred twenty-one".