18812121221 has 2 divisors, whose sum is σ = 18812121222. Its totient is φ = 18812121220.

The previous prime is 18812121187. The next prime is 18812121241. The reversal of 18812121221 is 12212121881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13701873025 + 5110248196 = 117055^2 + 71486^2 .

It is an emirp because it is prime and its reverse (12212121881) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18812121221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18812121241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9406060610 + 9406060611.

It is an arithmetic number, because the mean of its divisors is an integer number (9406060611).

Almost surely, 2^18812121221 is an apocalyptic number.

It is an amenable number.

18812121221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18812121221 is an equidigital number, since it uses as much as digits as its factorization.

18812121221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1024, while the sum is 29.

The spelling of 18812121221 in words is "eighteen billion, eight hundred twelve million, one hundred twenty-one thousand, two hundred twenty-one".