1665438138 has 128 divisors (see below), whose sum is σ = 4652605440. Its totient is φ = 429831360.

The previous prime is 1665438127. The next prime is 1665438143. The reversal of 1665438138 is 8318345661.

It is a junction number, because it is equal to n+sod(n) for n = 1665438093 and 1665438102.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 227353 + ... + 234563.

It is an arithmetic number, because the mean of its divisors is an integer number (36348480).

Almost surely, 2^1665438138 is an apocalyptic number.

1665438138 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1665438138, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2326302720).

1665438138 is an abundant number, since it is smaller than the sum of its proper divisors (2987167302).

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

1665438138 is a wasteful number, since it uses less digits than its factorization.

1665438138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7289 (or 7283 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The square root of 1665438138 is about 40809.7799307960. The cubic root of 1665438138 is about 1185.3397135300.

The spelling of 1665438138 in words is "one billion, six hundred sixty-five million, four hundred thirty-eight thousand, one hundred thirty-eight".