991128605 has 8 divisors (see below), whose sum is σ = 1195582464. Its totient is φ = 788750800.

The previous prime is 991128599. The next prime is 991128661. The reversal of 991128605 is 506821199.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 991128605 - 2⁸ = 991128349 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 517961 + ... + 519870.

It is an arithmetic number, because the mean of its divisors is an integer number (149447808).

Almost surely, 2^991128605 is an apocalyptic number.

It is an amenable number.

991128605 is a deficient number, since it is larger than the sum of its proper divisors (204453859).

991128605 is a wasteful number, since it uses less digits than its factorization.

991128605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1038027.

The product of its (nonzero) digits is 38880, while the sum is 41.

The square root of 991128605 is about 31482.1950473597. The cubic root of 991128605 is about 997.0340803507.

The spelling of 991128605 in words is "nine hundred ninety-one million, one hundred twenty-eight thousand, six hundred five".