1887991 has 4 divisors (see below), whose sum is σ = 2157712. Its totient is φ = 1618272.

The previous prime is 1887967. The next prime is 1888031. The reversal of 1887991 is 1997881.

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

It is a cyclic number.

It is not a de Polignac number, because 1887991 - 2¹¹ = 1885943 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1887091) 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, 134850 + ... + 134863.

It is an arithmetic number, because the mean of its divisors is an integer number (539428).

2^1887991 is an apocalyptic number.

1887991 is a deficient number, since it is larger than the sum of its proper divisors (269721).

1887991 is an equidigital number, since it uses as much as digits as its factorization.

1887991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269720.

The product of its digits is 36288, while the sum is 43.

The square root of 1887991 is about 1374.0418479799. The cubic root of 1887991 is about 123.5947357267.

The spelling of 1887991 in words is "one million, eight hundred eighty-seven thousand, nine hundred ninety-one".