99991111 has 8 divisors (see below), whose sum is σ = 110162448.
Its totient is φ = 90000000.
The previous prime is 99991109. The next prime is 99991207. The reversal of 99991111 is 11119999.
It can be divided in two parts, 9999 and 1111, that multiplied together give a square (11108889 = 33332).
It is a sphenic number, since it is the product of 3 distinct primes.
It is a 7-Lehmer number, since φ(99991111) divides (99991111-1)7.
It is a cyclic number.
It is not a de Polignac number, because 99991111 - 21 = 99991109 is a prime.
It is a nialpdrome in base 10.
It is a zygodrome in base 10.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (99995111) by changing a digit.
It is an upside-down number.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43890 + ... + 46111.
It is an arithmetic number, because the mean of its divisors is an integer number (13770306).
Almost surely, 299991111 is an apocalyptic number.
99991111 is a deficient number, since it is larger than the sum of its proper divisors (10171337).
99991111 is a wasteful number, since it uses less digits than its factorization.
99991111 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 90113.
The product of its digits is 6561, while the sum is 40.
The square root of 99991111 is about 9999.5555401228.
Note that the first 4 decimals coincide.
The cubic root of 99991111 is about 464.1451299260.
The spelling of 99991111 in words is "ninety-nine million, nine hundred ninety-one thousand, one hundred eleven".