20115810665 has 4 divisors (see below), whose sum is σ = 24138972804. Its totient is φ = 16092648528.

The previous prime is 20115810661. The next prime is 20115810697. The reversal of 20115810665 is 56601851102.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56601851102 = 2 ⋅28300925551.

It can be written as a sum of positive squares in 2 ways, for example, as 12418204969 + 7697605696 = 111437^2 + 87736^2 .

It is a cyclic number.

It is not a de Polignac number, because 20115810665 - 2² = 20115810661 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20115810661) 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, 2011581062 + ... + 2011581071.

It is an arithmetic number, because the mean of its divisors is an integer number (6034743201).

Almost surely, 2^20115810665 is an apocalyptic number.

It is an amenable number.

20115810665 is a deficient number, since it is larger than the sum of its proper divisors (4023162139).

20115810665 is an equidigital number, since it uses as much as digits as its factorization.

20115810665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4023162138.

The product of its (nonzero) digits is 14400, while the sum is 35.

The spelling of 20115810665 in words is "twenty billion, one hundred fifteen million, eight hundred ten thousand, six hundred sixty-five".