16721668555 has 4 divisors (see below), whose sum is σ = 20066002272. Its totient is φ = 13377334840.

The previous prime is 16721668517. The next prime is 16721668619. The reversal of 16721668555 is 55586612761.

It is a happy number.

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

It is not a de Polignac number, because 16721668555 - 2⁷ = 16721668427 is a prime.

It is a super-2 number, since 2×16721668555² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1672166851 + ... + 1672166860.

It is an arithmetic number, because the mean of its divisors is an integer number (5016500568).

Almost surely, 2^16721668555 is an apocalyptic number.

16721668555 is a deficient number, since it is larger than the sum of its proper divisors (3344333717).

16721668555 is an equidigital number, since it uses as much as digits as its factorization.

16721668555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3344333716.

The product of its digits is 3024000, while the sum is 52.

The spelling of 16721668555 in words is "sixteen billion, seven hundred twenty-one million, six hundred sixty-eight thousand, five hundred fifty-five".