16616721 has 16 divisors (see below), whose sum is σ = 24304320. Its totient is φ = 10014720.

The previous prime is 16616711. The next prime is 16616729. The reversal of 16616721 is 12761661.

It is not a de Polignac number, because 16616721 - 2⁶ = 16616657 is a prime.

It is a super-2 number, since 2×16616721² = 552230833583682, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (16616729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5065 + ... + 7673.

It is an arithmetic number, because the mean of its divisors is an integer number (1519020).

Almost surely, 2^16616721 is an apocalyptic number.

16616721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16616721 is a deficient number, since it is larger than the sum of its proper divisors (7687599).

16616721 is a wasteful number, since it uses less digits than its factorization.

16616721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2816.

The product of its digits is 3024, while the sum is 30.

The square root of 16616721 is about 4076.3612450321. The cubic root of 16616721 is about 255.1810632545.

The spelling of 16616721 in words is "sixteen million, six hundred sixteen thousand, seven hundred twenty-one".