2521665521 has 4 divisors (see below), whose sum is σ = 2522403492. Its totient is φ = 2520927552.

The previous prime is 2521665493. The next prime is 2521665527. The reversal of 2521665521 is 1255661252.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1589218225 + 932447296 = 39865^2 + 30536^2 .

It is a cyclic number.

It is not a de Polignac number, because 2521665521 - 2¹⁸ = 2521403377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2521665527) 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, 363836 + ... + 370701.

It is an arithmetic number, because the mean of its divisors is an integer number (630600873).

Almost surely, 2^2521665521 is an apocalyptic number.

It is an amenable number.

2521665521 is a deficient number, since it is larger than the sum of its proper divisors (737971).

2521665521 is an equidigital number, since it uses as much as digits as its factorization.

2521665521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 737970.

The product of its digits is 36000, while the sum is 35.

The square root of 2521665521 is about 50216.1878381862. The cubic root of 2521665521 is about 1361.1181550061.

The spelling of 2521665521 in words is "two billion, five hundred twenty-one million, six hundred sixty-five thousand, five hundred twenty-one".