991955 has 4 divisors (see below), whose sum is σ = 1190352. Its totient is φ = 793560.

The previous prime is 991951. The next prime is 991957. The reversal of 991955 is 559199.

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

It is not a de Polignac number, because 991955 - 2² = 991951 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99191 + ... + 99200.

It is an arithmetic number, because the mean of its divisors is an integer number (297588).

2⁹⁹¹⁹⁵⁵ is an apocalyptic number.

991955 is a deficient number, since it is larger than the sum of its proper divisors (198397).

991955 is a wasteful number, since it uses less digits than its factorization.

991955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198396.

The product of its digits is 18225, while the sum is 38.

The square root of 991955 is about 995.9693770393. The cubic root of 991955 is about 99.7311109683.

It can be divided in two parts, 9919 and 55, that multiplied together give a palindrome (545545).

The spelling of 991955 in words is "nine hundred ninety-one thousand, nine hundred fifty-five".