99991000 has 32 divisors (see below), whose sum is σ = 233981280. Its totient is φ = 39996000.

The previous prime is 99990973. The next prime is 99991009. The reversal of 99991000 is 19999.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99991009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48996 + ... + 50995.

It is an arithmetic number, because the mean of its divisors is an integer number (7311915).

Almost surely, 2^99991000 is an apocalyptic number.

It is an amenable number.

99991000 is an abundant number, since it is smaller than the sum of its proper divisors (133990280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

99991000 is a wasteful number, since it uses less digits than its factorization.

99991000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100012 (or 99998 counting only the distinct ones).

The product of its (nonzero) digits is 6561, while the sum is 37.

The square root of 99991000 is about 9999.5499898745. The cubic root of 99991000 is about 464.1449581770.

The spelling of 99991000 in words is "ninety-nine million, nine hundred ninety-one thousand".