1991955 has 32 divisors (see below), whose sum is σ = 3714048. Its totient is φ = 892800.

The previous prime is 1991947. The next prime is 1991959. The reversal of 1991955 is 5591991.

It is not a de Polignac number, because 1991955 - 2³ = 1991947 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1991959) 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 31 ways as a sum of consecutive naturals, for example, 6250 + ... + 6560.

It is an arithmetic number, because the mean of its divisors is an integer number (116064).

2^1991955 is an apocalyptic number.

1991955 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1991955 is a deficient number, since it is larger than the sum of its proper divisors (1722093).

1991955 is a wasteful number, since it uses less digits than its factorization.

1991955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 387.

The product of its digits is 18225, while the sum is 39.

The square root of 1991955 is about 1411.3663592420. The cubic root of 1991955 is about 125.8229435549.

The spelling of 1991955 in words is "one million, nine hundred ninety-one thousand, nine hundred fifty-five".