1999991 has 8 divisors (see below), whose sum is σ = 2334720. Its totient is φ = 1677528.

The previous prime is 1999979. The next prime is 1999993.

1999991 is nontrivially palindromic in base 10.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1999991 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1999993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2711 + ... + 3368.

It is an arithmetic number, because the mean of its divisors is an integer number (291840).

2^1999991 is an apocalyptic number.

1999991 is a deficient number, since it is larger than the sum of its proper divisors (334729).

1999991 is an equidigital number, since it uses as much as digits as its factorization.

1999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6133.

The product of its digits is 59049, while the sum is 47.

The square root of 1999991 is about 1414.2103803890. The cubic root of 1999991 is about 125.9919160010.

The spelling of 1999991 in words is "one million, nine hundred ninety-nine thousand, nine hundred ninety-one".