6615536537561 has 4 divisors (see below), whose sum is σ = 7560613185792. Its totient is φ = 5670459889332.

The previous prime is 6615536537539. The next prime is 6615536537573. The reversal of 6615536537561 is 1657356355166.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-6615536537561 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 6615536537561.

It is not an unprimeable number, because it can be changed into a prime (6615536737561) 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, 472538324105 + ... + 472538324118.

It is an arithmetic number, because the mean of its divisors is an integer number (1890153296448).

Almost surely, 2^{6615536537561} is an apocalyptic number.

It is an amenable number.

6615536537561 is a deficient number, since it is larger than the sum of its proper divisors (945076648231).

6615536537561 is an equidigital number, since it uses as much as digits as its factorization.

6615536537561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 945076648230.

The product of its digits is 51030000, while the sum is 59.

The spelling of 6615536537561 in words is "six trillion, six hundred fifteen billion, five hundred thirty-six million, five hundred thirty-seven thousand, five hundred sixty-one".