1861989 has 4 divisors (see below), whose sum is σ = 2482656. Its totient is φ = 1241324.

The previous prime is 1861973. The next prime is 1861991. The reversal of 1861989 is 9891681.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1861989 - 2⁴ = 1861973 is a prime.

It is a super-2 number, since 2×1861989² = 6934006072242, which contains 22 as substring.

It is a D-number.

It is a self number, because there is not a number n which added to its sum of digits gives 1861989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1861589) 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, 310329 + ... + 310334.

It is an arithmetic number, because the mean of its divisors is an integer number (620664).

2^1861989 is an apocalyptic number.

It is an amenable number.

1861989 is a deficient number, since it is larger than the sum of its proper divisors (620667).

1861989 is an equidigital number, since it uses as much as digits as its factorization.

1861989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 620666.

The product of its digits is 31104, while the sum is 42.

The square root of 1861989 is about 1364.5471776381. The cubic root of 1861989 is about 123.0247157683.

It can be divided in two parts, 1861 and 989, that added together give a triangular number (2850 = T₇₅).

The spelling of 1861989 in words is "one million, eight hundred sixty-one thousand, nine hundred eighty-nine".