1861987 has 4 divisors (see below), whose sum is σ = 1864720. Its totient is φ = 1859256.

The previous prime is 1861973. The next prime is 1861991. The reversal of 1861987 is 7891681.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 7891681 = 7 ⋅1127383.

It is a cyclic number.

It is not a de Polignac number, because 1861987 - 2⁷ = 1861859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1861927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 589 + ... + 2017.

It is an arithmetic number, because the mean of its divisors is an integer number (466180).

2^1861987 is an apocalyptic number.

1861987 is a deficient number, since it is larger than the sum of its proper divisors (2733).

1861987 is a wasteful number, since it uses less digits than its factorization.

1861987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2732.

The product of its digits is 24192, while the sum is 40.

The square root of 1861987 is about 1364.5464447940. The cubic root of 1861987 is about 123.0246717205.

The spelling of 1861987 in words is "one million, eight hundred sixty-one thousand, nine hundred eighty-seven".