1991920 has 40 divisors (see below), whose sum is σ = 5294304. Its totient is φ = 682752.

The previous prime is 1991911. The next prime is 1991921. The reversal of 1991920 is 291991.

It is a tau number, because it is divible by the number of its divisors (40).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991921) 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, 1219 + ... + 2338.

2^1991920 is an apocalyptic number.

1991920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1991920 is an abundant number, since it is smaller than the sum of its proper divisors (3302384).

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

1991920 is a wasteful number, since it uses less digits than its factorization.

1991920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3577 (or 3571 counting only the distinct ones).

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 1991920 is about 1411.3539598556. The cubic root of 1991920 is about 125.8222066191.

The spelling of 1991920 in words is "one million, nine hundred ninety-one thousand, nine hundred twenty".