899999999991 has 20 divisors (see below), whose sum is σ = 1344509166000. Its totient is φ = 599971116096.

The previous prime is 899999999981. The next prime is 900000000013. The reversal of 899999999991 is 199999999998.

It is not a de Polignac number, because 899999999991 - 2⁵ = 899999999959 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 899999999892 and 899999999901.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (899999999981) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1496950 + ... + 2010188.

It is an arithmetic number, because the mean of its divisors is an integer number (67225458300).

Almost surely, 2^899999999991 is an apocalyptic number.

899999999991 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

899999999991 is a deficient number, since it is larger than the sum of its proper divisors (444509166009).

899999999991 is a wasteful number, since it uses less digits than its factorization.

899999999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 534900 (or 534891 counting only the distinct ones).

The product of its digits is 27894275208, while the sum is 99.

It can be divided in two parts, 89999999999 and 1, that added together give a square (90000000000 = 300000²).

The spelling of 899999999991 in words is "eight hundred ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety-one".