1000000221991 has 2 divisors, whose sum is σ = 1000000221992. Its totient is φ = 1000000221990.

The previous prime is 1000000221977. The next prime is 1000000222003. The reversal of 1000000221991 is 1991220000001.

1000000221991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is an emirp because it is prime and its reverse (1991220000001) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1000000221991 - 2²⁹ = 999463351079 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1000000221691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 500000110995 + 500000110996.

It is an arithmetic number, because the mean of its divisors is an integer number (500000110996).

Almost surely, 2^{1000000221991} is an apocalyptic number.

1000000221991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1000000221991 is an equidigital number, since it uses as much as digits as its factorization.

1000000221991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 25.

Adding to 1000000221991 its reverse (1991220000001), we get a palindrome (2991220221992).

The spelling of 1000000221991 in words is "one trillion, two hundred twenty-one thousand, nine hundred ninety-one".