16511515561 has 4 divisors (see below), whose sum is σ = 16511879124. Its totient is φ = 16511152000.

The previous prime is 16511515511. The next prime is 16511515571. The reversal of 16511515561 is 16551511561.

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 15035419161 + 1476096400 = 122619^2 + 38420^2 .

It is a cyclic number.

It is not a de Polignac number, because 16511515561 - 2²³ = 16503126953 is a prime.

It is a super-2 number, since 2×16511515561² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16511515561.

It is not an unprimeable number, because it can be changed into a prime (16511515511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 101980 + ... + 208381.

It is an arithmetic number, because the mean of its divisors is an integer number (4127969781).

Almost surely, 2^16511515561 is an apocalyptic number.

It is an amenable number.

16511515561 is a deficient number, since it is larger than the sum of its proper divisors (363563).

16511515561 is an equidigital number, since it uses as much as digits as its factorization.

16511515561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363562.

The product of its digits is 22500, while the sum is 37.

The spelling of 16511515561 in words is "sixteen billion, five hundred eleven million, five hundred fifteen thousand, five hundred sixty-one".