221011121211821 has 2 divisors, whose sum is σ = 221011121211822. Its totient is φ = 221011121211820.

The previous prime is 221011121211701. The next prime is 221011121211857. The reversal of 221011121211821 is 128112121110122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 115843245302500 + 105167875909321 = 10763050^2 + 10255139^2 .

It is a cyclic number.

It is not a de Polignac number, because 221011121211821 - 2¹⁴ = 221011121195437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221011121210821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110505560605910 + 110505560605911.

It is an arithmetic number, because the mean of its divisors is an integer number (110505560605911).

Almost surely, 2^{221011121211821} is an apocalyptic number.

It is an amenable number.

221011121211821 is a deficient number, since it is larger than the sum of its proper divisors (1).

221011121211821 is an equidigital number, since it uses as much as digits as its factorization.

221011121211821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 256, while the sum is 26.

Adding to 221011121211821 its reverse (128112121110122), we get a palindrome (349123242321943).

The spelling of 221011121211821 in words is "two hundred twenty-one trillion, eleven billion, one hundred twenty-one million, two hundred eleven thousand, eight hundred twenty-one".