991530 has 48 divisors (see below), whose sum is σ = 2695680. Its totient is φ = 252384.

The previous prime is 991511. The next prime is 991531. The reversal of 991530 is 35199.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 991494 and 991503.

It is not an unprimeable number, because it can be changed into a prime (991531) by changing a digit.

991530 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1831 + ... + 2309.

It is an arithmetic number, because the mean of its divisors is an integer number (56160).

2⁹⁹¹⁵³⁰ is an apocalyptic number.

991530 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 991530, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1347840).

991530 is an abundant number, since it is smaller than the sum of its proper divisors (1704150).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991530 is a wasteful number, since it uses less digits than its factorization.

991530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 515 (or 512 counting only the distinct ones).

The product of its (nonzero) digits is 1215, while the sum is 27.

The square root of 991530 is about 995.7559942074. The cubic root of 991530 is about 99.7168657733.

It can be divided in two parts, 991 and 530, that added together give a square (1521 = 39²).

The spelling of 991530 in words is "nine hundred ninety-one thousand, five hundred thirty".