16661868506 has 4 divisors (see below), whose sum is σ = 24992802762. Its totient is φ = 8330934252.

The previous prime is 16661868497. The next prime is 16661868523. The reversal of 16661868506 is 60586816661.

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

It can be written as a sum of positive squares in only one way, i.e., 16463199481 + 198669025 = 128309^2 + 14095^2 .

It is a super-2 number, since 2×16661868506² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4165467125 + ... + 4165467128.

Almost surely, 2^16661868506 is an apocalyptic number.

16661868506 is a deficient number, since it is larger than the sum of its proper divisors (8330934256).

16661868506 is an equidigital number, since it uses as much as digits as its factorization.

16661868506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8330934255.

The product of its (nonzero) digits is 2488320, while the sum is 53.

The spelling of 16661868506 in words is "sixteen billion, six hundred sixty-one million, eight hundred sixty-eight thousand, five hundred six".