991087 has 4 divisors (see below), whose sum is σ = 994896. Its totient is φ = 987280.

The previous prime is 991079. The next prime is 991091. The reversal of 991087 is 780199.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991087 - 2³ = 991079 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1483 + ... + 2044.

It is an arithmetic number, because the mean of its divisors is an integer number (248724).

2⁹⁹¹⁰⁸⁷ is an apocalyptic number.

991087 is a deficient number, since it is larger than the sum of its proper divisors (3809).

991087 is a wasteful number, since it uses less digits than its factorization.

991087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3808.

The product of its (nonzero) digits is 4536, while the sum is 34.

The square root of 991087 is about 995.5335253019. The cubic root of 991087 is about 99.7020129190.

The spelling of 991087 in words is "nine hundred ninety-one thousand, eighty-seven".