1915991 has 16 divisors (see below), whose sum is σ = 2419200. Its totient is φ = 1474080.

The previous prime is 1915981. The next prime is 1915993. The reversal of 1915991 is 1995191.

It is a cyclic number.

It is not a de Polignac number, because 1915991 - 2¹⁰ = 1914967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1915993) 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 15 ways as a sum of consecutive naturals, for example, 11390 + ... + 11556.

It is an arithmetic number, because the mean of its divisors is an integer number (151200).

2^1915991 is an apocalyptic number.

1915991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1915991 is a deficient number, since it is larger than the sum of its proper divisors (503209).

1915991 is a wasteful number, since it uses less digits than its factorization.

1915991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 334.

The product of its digits is 3645, while the sum is 35.

The square root of 1915991 is about 1384.1932668526. The cubic root of 1915991 is about 124.2027337432.

The spelling of 1915991 in words is "one million, nine hundred fifteen thousand, nine hundred ninety-one".