16505133581 has 2 divisors, whose sum is σ = 16505133582. Its totient is φ = 16505133580.

The previous prime is 16505133529. The next prime is 16505133583. The reversal of 16505133581 is 18533150561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15268556356 + 1236577225 = 123566^2 + 35165^2 .

It is an emirp because it is prime and its reverse (18533150561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16505133581 - 2²⁶ = 16438024717 is a prime.

It is a super-2 number, since 2×16505133581² (a number of 21 digits) contains 22 as substring.

Together with 16505133583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16505133583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8252566790 + 8252566791.

It is an arithmetic number, because the mean of its divisors is an integer number (8252566791).

Almost surely, 2^16505133581 is an apocalyptic number.

It is an amenable number.

16505133581 is a deficient number, since it is larger than the sum of its proper divisors (1).

16505133581 is an equidigital number, since it uses as much as digits as its factorization.

16505133581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 54000, while the sum is 38.

The spelling of 16505133581 in words is "sixteen billion, five hundred five million, one hundred thirty-three thousand, five hundred eighty-one".