16721666685 has 24 divisors (see below), whose sum is σ = 29531098584. Its totient is φ = 8749952640.

The previous prime is 16721666683. The next prime is 16721666711. The reversal of 16721666685 is 58666612761.

It can be written as a sum of positive squares in 4 ways, for example, as 961124004 + 15760542681 = 31002^2 + 125541^2 .

It is not a de Polignac number, because 16721666685 - 2¹ = 16721666683 is a prime.

It is a super-2 number, since 2×16721666685² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16721666683) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3503206 + ... + 3507975.

It is an arithmetic number, because the mean of its divisors is an integer number (1230462441).

Almost surely, 2^16721666685 is an apocalyptic number.

16721666685 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

16721666685 is a deficient number, since it is larger than the sum of its proper divisors (12809431899).

16721666685 is a wasteful number, since it uses less digits than its factorization.

16721666685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7011245 (or 7011242 counting only the distinct ones).

The product of its digits is 4354560, while the sum is 54.

The spelling of 16721666685 in words is "sixteen billion, seven hundred twenty-one million, six hundred sixty-six thousand, six hundred eighty-five".