1991210122201 has 4 divisors (see below), whose sum is σ = 1994523284404. Its totient is φ = 1987896960000.

The previous prime is 1991210122199. The next prime is 1991210122273. The reversal of 1991210122201 is 1022210121991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1676892912601 + 314317209600 = 1294949^2 + 560640^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991210122201 - 2¹ = 1991210122199 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991210122301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1656580200 + ... + 1656581401.

It is an arithmetic number, because the mean of its divisors is an integer number (498630821101).

Almost surely, 2^{1991210122201} is an apocalyptic number.

It is an amenable number.

1991210122201 is a deficient number, since it is larger than the sum of its proper divisors (3313162203).

1991210122201 is an equidigital number, since it uses as much as digits as its factorization.

1991210122201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3313162202.

The product of its (nonzero) digits is 1296, while the sum is 31.

The spelling of 1991210122201 in words is "one trillion, nine hundred ninety-one billion, two hundred ten million, one hundred twenty-two thousand, two hundred one".