221012121809 has 2 divisors, whose sum is σ = 221012121810. Its totient is φ = 221012121808.

The previous prime is 221012121779. The next prime is 221012121829. The reversal of 221012121809 is 908121210122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 164063072209 + 56949049600 = 405047^2 + 238640^2 .

It is a cyclic number.

It is not a de Polignac number, because 221012121809 - 2²⁰ = 221011073233 is a prime.

It is not a weakly prime, because it can be changed into another prime (221012121829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110506060904 + 110506060905.

It is an arithmetic number, because the mean of its divisors is an integer number (110506060905).

Almost surely, 2^221012121809 is an apocalyptic number.

It is an amenable number.

221012121809 is a deficient number, since it is larger than the sum of its proper divisors (1).

221012121809 is an equidigital number, since it uses as much as digits as its factorization.

221012121809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 29.

The spelling of 221012121809 in words is "two hundred twenty-one billion, twelve million, one hundred twenty-one thousand, eight hundred nine".