991199019901 has 4 divisors (see below), whose sum is σ = 992239103772. Its totient is φ = 990158936032.

The previous prime is 991199019893. The next prime is 991199019919. The reversal of 991199019901 is 109910991199.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 109910991199 = 19553 ⋅5621183.

It can be written as a sum of positive squares in 2 ways, for example, as 689414696100 + 301784323801 = 830310^2 + 549349^2 .

It is a cyclic number.

It is not a de Polignac number, because 991199019901 - 2³ = 991199019893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991199019971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 520040506 + ... + 520042411.

It is an arithmetic number, because the mean of its divisors is an integer number (248059775943).

Almost surely, 2^991199019901 is an apocalyptic number.

It is an amenable number.

991199019901 is a deficient number, since it is larger than the sum of its proper divisors (1040083871).

991199019901 is a wasteful number, since it uses less digits than its factorization.

991199019901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1040083870.

The product of its (nonzero) digits is 531441, while the sum is 58.

The spelling of 991199019901 in words is "nine hundred ninety-one billion, one hundred ninety-nine million, nineteen thousand, nine hundred one".