1987865 has 16 divisors (see below), whose sum is σ = 2661120. Its totient is φ = 1413120.

The previous prime is 1987849. The next prime is 1987873. The reversal of 1987865 is 5687891.

1987865 = 140² + 141² + ... + 205².

It is a happy number.

It is not a de Polignac number, because 1987865 - 2⁴ = 1987849 is a prime.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 2201 + ... + 2969.

It is an arithmetic number, because the mean of its divisors is an integer number (166320).

2^1987865 is an apocalyptic number.

It is an amenable number.

1987865 is a deficient number, since it is larger than the sum of its proper divisors (673255).

1987865 is a wasteful number, since it uses less digits than its factorization.

1987865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 832.

The product of its digits is 120960, while the sum is 44.

The square root of 1987865 is about 1409.9166642040. The cubic root of 1987865 is about 125.7367688414.

The spelling of 1987865 in words is "one million, nine hundred eighty-seven thousand, eight hundred sixty-five".