1665881101 has 4 divisors (see below), whose sum is σ = 1666047100. Its totient is φ = 1665715104.

The previous prime is 1665881089. The next prime is 1665881123. The reversal of 1665881101 is 1011885661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1011885661 = 29 ⋅34892609.

It can be written as a sum of positive squares in 2 ways, for example, as 458388100 + 1207493001 = 21410^2 + 34749^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665881101 - 2¹³ = 1665872909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665881171) 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, 66906 + ... + 88363.

It is an arithmetic number, because the mean of its divisors is an integer number (416511775).

Almost surely, 2^1665881101 is an apocalyptic number.

It is an amenable number.

1665881101 is a deficient number, since it is larger than the sum of its proper divisors (165999).

1665881101 is a wasteful number, since it uses less digits than its factorization.

1665881101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165998.

The product of its (nonzero) digits is 11520, while the sum is 37.

The square root of 1665881101 is about 40815.2067371954. The cubic root of 1665881101 is about 1185.4447940049. Note that the first 3 decimals are identical.

The spelling of 1665881101 in words is "one billion, six hundred sixty-five million, eight hundred eighty-one thousand, one hundred one".