1991500 has 48 divisors (see below), whose sum is σ = 4979520. Its totient is φ = 681600.

The previous prime is 1991491. The next prime is 1991503. The reversal of 1991500 is 51991.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is not an unprimeable number, because it can be changed into a prime (1991503) 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 15 ways as a sum of consecutive naturals, for example, 3216 + ... + 3784.

It is an arithmetic number, because the mean of its divisors is an integer number (103740).

2^1991500 is an apocalyptic number.

1991500 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1991500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2489760).

1991500 is an abundant number, since it is smaller than the sum of its proper divisors (2988020).

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

1991500 is a wasteful number, since it uses less digits than its factorization.

1991500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 595 (or 583 counting only the distinct ones).

The product of its (nonzero) digits is 405, while the sum is 25.

The square root of 1991500 is about 1411.2051587207. The cubic root of 1991500 is about 125.8133627162.

It can be divided in two parts, 19 and 91500, that added together give a palindrome (91519).

The spelling of 1991500 in words is "one million, nine hundred ninety-one thousand, five hundred".