16521665507 has 4 divisors (see below), whose sum is σ = 16521937560. Its totient is φ = 16521393456.

The previous prime is 16521665473. The next prime is 16521665527. The reversal of 16521665507 is 70556612561.

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

It is a cyclic number.

It is not a de Polignac number, because 16521665507 - 2¹² = 16521661411 is a prime.

It is a super-2 number, since 2×16521665507² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16521665527) 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, 1244 + ... + 181782.

It is an arithmetic number, because the mean of its divisors is an integer number (4130484390).

Almost surely, 2^16521665507 is an apocalyptic number.

16521665507 is a deficient number, since it is larger than the sum of its proper divisors (272053).

16521665507 is an equidigital number, since it uses as much as digits as its factorization.

16521665507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272052.

The product of its (nonzero) digits is 378000, while the sum is 44.

The spelling of 16521665507 in words is "sixteen billion, five hundred twenty-one million, six hundred sixty-five thousand, five hundred seven".