1221001110991 has 2 divisors, whose sum is σ = 1221001110992. Its totient is φ = 1221001110990.

The previous prime is 1221001110977. The next prime is 1221001111013. The reversal of 1221001110991 is 1990111001221.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1221001110991 - 2¹³ = 1221001102799 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221001110911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610500555495 + 610500555496.

It is an arithmetic number, because the mean of its divisors is an integer number (610500555496).

Almost surely, 2^{1221001110991} is an apocalyptic number.

1221001110991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221001110991 is an equidigital number, since it uses as much as digits as its factorization.

1221001110991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 28.

The spelling of 1221001110991 in words is "one trillion, two hundred twenty-one billion, one million, one hundred ten thousand, nine hundred ninety-one".