1861866 has 28 divisors (see below), whose sum is σ = 4190562. Its totient is φ = 620136.

The previous prime is 1861861. The next prime is 1861879. The reversal of 1861866 is 6681681.

It can be written as a sum of positive squares in only one way, i.e., 1476225 + 385641 = 1215^2 + 621^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 1861866.

It is not an unprimeable number, because it can be changed into a prime (1861861) 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 13 ways as a sum of consecutive naturals, for example, 820 + ... + 2096.

2^1861866 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1861866, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2095281).

1861866 is an abundant number, since it is smaller than the sum of its proper divisors (2328696).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1861866 is an equidigital number, since it uses as much as digits as its factorization.

1861866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1297 (or 1282 counting only the distinct ones).

The product of its digits is 13824, while the sum is 36.

The square root of 1861866 is about 1364.5021069973. The cubic root of 1861866 is about 123.0220067703.

The spelling of 1861866 in words is "one million, eight hundred sixty-one thousand, eight hundred sixty-six".