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990991 = 4432237
BaseRepresentation
bin11110001111100001111
31212100101101
43301330033
5223202431
633123531
711265121
oct3617417
91770341
10990991
11617601
123b95a7
132890b1
141bb211
15148961
hexf1f0f

990991 has 4 divisors (see below), whose sum is σ = 993672. Its totient is φ = 988312.

The previous prime is 990989. The next prime is 991009. The reversal of 990991 is 199099.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199099 = 1031933.

It is a cyclic number.

It is not a de Polignac number, because 990991 - 21 = 990989 is a prime.

It is a Duffinian number.

990991 is a lucky number.

It is a zygodrome in base 2.

It is a self number, because there is not a number n which added to its sum of digits gives 990991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (990961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 676 + ... + 1561.

It is an arithmetic number, because the mean of its divisors is an integer number (248418).

2990991 is an apocalyptic number.

990991 is a deficient number, since it is larger than the sum of its proper divisors (2681).

990991 is a wasteful number, since it uses less digits than its factorization.

990991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2680.

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

The square root of 990991 is about 995.4853087816. The cubic root of 990991 is about 99.6987936583.

It can be divided in two parts, 9909 and 91, that added together give a 4-th power (10000 = 104).

The spelling of 990991 in words is "nine hundred ninety thousand, nine hundred ninety-one".

Divisors: 1 443 2237 990991