9891991990 has 32 divisors (see below), whose sum is σ = 17962560000. Its totient is φ = 3922006368.

The previous prime is 9891991987. The next prime is 9891991999. The reversal of 9891991990 is 991991989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9891991999) 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 15 ways as a sum of consecutive naturals, for example, 910611 + ... + 921409.

It is an arithmetic number, because the mean of its divisors is an integer number (561330000).

Almost surely, 2^9891991990 is an apocalyptic number.

9891991990 is a deficient number, since it is larger than the sum of its proper divisors (8070568010).

9891991990 is a wasteful number, since it uses less digits than its factorization.

9891991990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11604.

The product of its (nonzero) digits is 4251528, while the sum is 64.

The square root of 9891991990 is about 99458.4938052050. The cubic root of 9891991990 is about 2146.6500555160.

The spelling of 9891991990 in words is "nine billion, eight hundred ninety-one million, nine hundred ninety-one thousand, nine hundred ninety".