1866639636 has 72 divisors (see below), whose sum is σ = 5000322600. Its totient is φ = 586091520.

The previous prime is 1866639623. The next prime is 1866639637. The reversal of 1866639636 is 6369366681.

It can be written as a sum of positive squares in 4 ways, for example, as 38564100 + 1828075536 = 6210^2 + 42756^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1866639637) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21000 + ... + 64608.

It is an arithmetic number, because the mean of its divisors is an integer number (69448925).

Almost surely, 2^1866639636 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1866639636, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2500161300).

1866639636 is an abundant number, since it is smaller than the sum of its proper divisors (3133682964).

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

1866639636 is a wasteful number, since it uses less digits than its factorization.

1866639636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43689 (or 43684 counting only the distinct ones).

The product of its digits is 5038848, while the sum is 54.

The square root of 1866639636 is about 43204.6251690719. The cubic root of 1866639636 is about 1231.2705570155.

The spelling of 1866639636 in words is "one billion, eight hundred sixty-six million, six hundred thirty-nine thousand, six hundred thirty-six".