1991995 has 8 divisors (see below), whose sum is σ = 2409984. Its totient is φ = 1580544.

The previous prime is 1991993. The next prime is 1991999. The reversal of 1991995 is 5991991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1991995 - 2¹ = 1991993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 934 + ... + 2203.

It is an arithmetic number, because the mean of its divisors is an integer number (301248).

2^1991995 is an apocalyptic number.

1991995 is a deficient number, since it is larger than the sum of its proper divisors (417989).

1991995 is a wasteful number, since it uses less digits than its factorization.

1991995 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3269.

The product of its digits is 32805, while the sum is 43.

The square root of 1991995 is about 1411.3805298359. The cubic root of 1991995 is about 125.8237857567.

It can be divided in two parts, 1991 and 995, that multiplied together give a triangular number (1981045 = T₁₉₉₀).

The spelling of 1991995 in words is "one million, nine hundred ninety-one thousand, nine hundred ninety-five".