2103121665 has 20 divisors (see below), whose sum is σ = 3770041044. Its totient is φ = 1121664672.

The previous prime is 2103121637. The next prime is 2103121667. The reversal of 2103121665 is 5661213012.

It can be written as a sum of positive squares in 2 ways, for example, as 971942976 + 1131178689 = 31176^2 + 33633^2 .

It is not a de Polignac number, because 2103121665 - 2⁸ = 2103121409 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2103121667) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 2596042 + ... + 2596851.

Almost surely, 2^2103121665 is an apocalyptic number.

It is an amenable number.

2103121665 is a deficient number, since it is larger than the sum of its proper divisors (1666919379).

2103121665 is an equidigital number, since it uses as much as digits as its factorization.

2103121665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5192910 (or 5192901 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 2103121665 is about 45859.8044588068. The cubic root of 2103121665 is about 1281.2133808610.

Adding to 2103121665 its reverse (5661213012), we get a palindrome (7764334677).

The spelling of 2103121665 in words is "two billion, one hundred three million, one hundred twenty-one thousand, six hundred sixty-five".