1919991 has 4 divisors (see below), whose sum is σ = 2559992. Its totient is φ = 1279992.

The previous prime is 1919987. The next prime is 1920001. The reversal of 1919991 is 1999191.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 1919991 - 2² = 1919987 is a prime.

It is a super-3 number, since 3×1919991³ = 21233365402999677813, which contains 333 as substring.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1919591) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 319996 + ... + 320001.

It is an arithmetic number, because the mean of its divisors is an integer number (639998).

2^1919991 is an apocalyptic number.

1919991 is a deficient number, since it is larger than the sum of its proper divisors (640001).

1919991 is an equidigital number, since it uses as much as digits as its factorization.

1919991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 640000.

The product of its digits is 6561, while the sum is 39.

The square root of 1919991 is about 1385.6373984560. The cubic root of 1919991 is about 124.2891060358.

The spelling of 1919991 in words is "one million, nine hundred nineteen thousand, nine hundred ninety-one".