1666738665 has 24 divisors (see below), whose sum is σ = 2890123080. Its totient is φ = 888585984.

The previous prime is 1666738651. The next prime is 1666738669. The reversal of 1666738665 is 5668376661.

It can be written as a sum of positive squares in 4 ways, for example, as 73770921 + 1592967744 = 8589^2 + 39912^2 .

It is not a de Polignac number, because 1666738665 - 2²² = 1662544361 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1666738669) 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, 149091 + ... + 159879.

It is an arithmetic number, because the mean of its divisors is an integer number (120421795).

Almost surely, 2^1666738665 is an apocalyptic number.

1666738665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1666738665 is a deficient number, since it is larger than the sum of its proper divisors (1223384415).

1666738665 is a wasteful number, since it uses less digits than its factorization.

1666738665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14233 (or 14230 counting only the distinct ones).

The product of its digits is 6531840, while the sum is 54.

The square root of 1666738665 is about 40825.7108327583. The cubic root of 1666738665 is about 1185.6481739435.

The spelling of 1666738665 in words is "one billion, six hundred sixty-six million, seven hundred thirty-eight thousand, six hundred sixty-five".