21111220121021 has 2 divisors, whose sum is σ = 21111220121022. Its totient is φ = 21111220121020.

The previous prime is 21111220121003. The next prime is 21111220121171. The reversal of 21111220121021 is 12012102211112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17126445604921 + 3984774516100 = 4138411^2 + 1996190^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21111220121021 is a prime.

It is a super-2 number, since 2×21111220121021² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111220141021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555610060510 + 10555610060511.

It is an arithmetic number, because the mean of its divisors is an integer number (10555610060511).

Almost surely, 2^{21111220121021} is an apocalyptic number.

It is an amenable number.

21111220121021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111220121021 is an equidigital number, since it uses as much as digits as its factorization.

21111220121021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 17.

Adding to 21111220121021 its reverse (12012102211112), we get a palindrome (33123322332133).

The spelling of 21111220121021 in words is "twenty-one trillion, one hundred eleven billion, two hundred twenty million, one hundred twenty-one thousand, twenty-one".