991549 has 8 divisors (see below), whose sum is σ = 1081080. Its totient is φ = 903936.

The previous prime is 991547. The next prime is 991567. The reversal of 991549 is 945199.

It can be written as a sum of positive squares in 4 ways, for example, as 79524 + 912025 = 282^2 + 955^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 991549 - 2¹ = 991547 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991541) 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 7 ways as a sum of consecutive naturals, for example, 729 + ... + 1585.

It is an arithmetic number, because the mean of its divisors is an integer number (135135).

2⁹⁹¹⁵⁴⁹ is an apocalyptic number.

It is an amenable number.

991549 is a deficient number, since it is larger than the sum of its proper divisors (89531).

991549 is a wasteful number, since it uses less digits than its factorization.

991549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 959.

The product of its digits is 14580, while the sum is 37.

The square root of 991549 is about 995.7655346516. The cubic root of 991549 is about 99.7175027043.

It can be divided in two parts, 991 and 549, that added together give a triangular number (1540 = T₅₅).

The spelling of 991549 in words is "nine hundred ninety-one thousand, five hundred forty-nine".