9001009991 has 4 divisors (see below), whose sum is σ = 9291365184. Its totient is φ = 8710654800.

The previous prime is 9001009967. The next prime is 9001009999. The reversal of 9001009991 is 1999001009.

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: 1999001009 = 1367 ⋅1462327.

It is a cyclic number.

It is not a de Polignac number, because 9001009991 - 2¹⁰ = 9001008967 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 (9001009999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 145177550 + ... + 145177611.

It is an arithmetic number, because the mean of its divisors is an integer number (2322841296).

Almost surely, 2^9001009991 is an apocalyptic number.

9001009991 is a deficient number, since it is larger than the sum of its proper divisors (290355193).

9001009991 is a wasteful number, since it uses less digits than its factorization.

9001009991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290355192.

The product of its (nonzero) digits is 6561, while the sum is 38.

The square root of 9001009991 is about 94873.6527756785. The cubic root of 9001009991 is about 2080.1616299911.

The spelling of 9001009991 in words is "nine billion, one million, nine thousand, nine hundred ninety-one".