1665126605 has 4 divisors (see below), whose sum is σ = 1998151932. Its totient is φ = 1332101280.

The previous prime is 1665126601. The next prime is 1665126613. The reversal of 1665126605 is 5066215661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5066215661 = 13 ⋅389708897.

It can be written as a sum of positive squares in 2 ways, for example, as 206726884 + 1458399721 = 14378^2 + 38189^2 .

It is not a de Polignac number, because 1665126605 - 2² = 1665126601 is a prime.

It is a super-2 number, since 2×1665126605² = 5545293221357652050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665126601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166512656 + ... + 166512665.

It is an arithmetic number, because the mean of its divisors is an integer number (499537983).

Almost surely, 2^1665126605 is an apocalyptic number.

It is an amenable number.

1665126605 is a deficient number, since it is larger than the sum of its proper divisors (333025327).

1665126605 is an equidigital number, since it uses as much as digits as its factorization.

1665126605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333025326.

The product of its (nonzero) digits is 64800, while the sum is 38.

The square root of 1665126605 is about 40805.9628608369. The cubic root of 1665126605 is about 1185.2657999541.

The spelling of 1665126605 in words is "one billion, six hundred sixty-five million, one hundred twenty-six thousand, six hundred five".