1991604 has 48 divisors (see below), whose sum is σ = 4939200. Its totient is φ = 623616.

The previous prime is 1991603. The next prime is 1991609. The reversal of 1991604 is 4061991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991603) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20484 + ... + 20580.

It is an arithmetic number, because the mean of its divisors is an integer number (102900).

2^1991604 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1991604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2469600).

1991604 is an abundant number, since it is smaller than the sum of its proper divisors (2947596).

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

1991604 is a wasteful number, since it uses less digits than its factorization.

1991604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 1991604 is about 1411.2420061775. The cubic root of 1991604 is about 125.8155527508.

The spelling of 1991604 in words is "one million, nine hundred ninety-one thousand, six hundred four".