1666500138 has 24 divisors (see below), whose sum is σ = 3735260100. Its totient is φ = 536344704.

The previous prime is 1666500079. The next prime is 1666500161. The reversal of 1666500138 is 8310056661.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 1654618329 + 11881809 = 40677^2 + 3447^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1595743 + ... + 1596786.

Almost surely, 2^1666500138 is an apocalyptic number.

1666500138 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1666500138 is an abundant number, since it is smaller than the sum of its proper divisors (2068759962).

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

1666500138 is a wasteful number, since it uses less digits than its factorization.

1666500138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3192566 (or 3192563 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 1666500138 is about 40822.7894441328. The cubic root of 1666500138 is about 1185.5916118681.

Adding to 1666500138 its reverse (8310056661), we get a palindrome (9976556799).

The spelling of 1666500138 in words is "one billion, six hundred sixty-six million, five hundred thousand, one hundred thirty-eight".