1991964 has 36 divisors (see below), whose sum is σ = 5050136. Its totient is φ = 607488.

The previous prime is 1991963. The next prime is 1991989. The reversal of 1991964 is 4691991.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991963) 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 11 ways as a sum of consecutive naturals, for example, 17572 + ... + 17684.

2^1991964 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 1991964, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2525068).

1991964 is an abundant number, since it is smaller than the sum of its proper divisors (3058172).

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

1991964 is a wasteful number, since it uses less digits than its factorization.

1991964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246 (or 131 counting only the distinct ones).

The product of its digits is 17496, while the sum is 39.

The square root of 1991964 is about 1411.3695476380. The cubic root of 1991964 is about 125.8231330513.

Multiplying 1991964 by its sum of digits (39), we get a square (77686596 = 8814²).

1991964 divided by its sum of digits (39) gives a square (51076 = 226²).

The spelling of 1991964 in words is "one million, nine hundred ninety-one thousand, nine hundred sixty-four".