16166721 has 4 divisors (see below), whose sum is σ = 21555632. Its totient is φ = 10777812.

The previous prime is 16166707. The next prime is 16166741. The reversal of 16166721 is 12766161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12766161 = 3 ⋅4255387.

It is not a de Polignac number, because 16166721 - 2⁹ = 16166209 is a prime.

It is a super-2 number, since 2×16166721² = 522725735783682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16166741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2694451 + ... + 2694456.

It is an arithmetic number, because the mean of its divisors is an integer number (5388908).

Almost surely, 2^16166721 is an apocalyptic number.

It is an amenable number.

16166721 is a deficient number, since it is larger than the sum of its proper divisors (5388911).

16166721 is an equidigital number, since it uses as much as digits as its factorization.

16166721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5388910.

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

The square root of 16166721 is about 4020.7861171666. The cubic root of 16166721 is about 252.8564178764.

The spelling of 16166721 in words is "sixteen million, one hundred sixty-six thousand, seven hundred twenty-one".