20111221021 has 2 divisors, whose sum is σ = 20111221022. Its totient is φ = 20111221020.

The previous prime is 20111221003. The next prime is 20111221057. The reversal of 20111221021 is 12012211102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19520001796 + 591219225 = 139714^2 + 24315^2 .

It is a cyclic number.

It is not a de Polignac number, because 20111221021 - 2²¹ = 20109123869 is a prime.

It is a super-2 number, since 2×20111221021² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20111220992 and 20111221010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20111221121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10055610510 + 10055610511.

It is an arithmetic number, because the mean of its divisors is an integer number (10055610511).

Almost surely, 2^20111221021 is an apocalyptic number.

It is an amenable number.

20111221021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20111221021 is an equidigital number, since it uses as much as digits as its factorization.

20111221021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 20111221021 its reverse (12012211102), we get a palindrome (32123432123).

The spelling of 20111221021 in words is "twenty billion, one hundred eleven million, two hundred twenty-one thousand, twenty-one".