16500721 has 4 divisors (see below), whose sum is σ = 17369200. Its totient is φ = 15632244.

The previous prime is 16500709. The next prime is 16500733. The reversal of 16500721 is 12700561.

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.

It is an interprime number because it is at equal distance from previous prime (16500709) and next prime (16500733).

It is a cyclic number.

It is not a de Polignac number, because 16500721 - 2⁷ = 16500593 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16500692 and 16500701.

It is not an unprimeable number, because it can be changed into a prime (16500751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 434211 + ... + 434248.

It is an arithmetic number, because the mean of its divisors is an integer number (4342300).

Almost surely, 2^16500721 is an apocalyptic number.

It is an amenable number.

16500721 is a deficient number, since it is larger than the sum of its proper divisors (868479).

16500721 is an equidigital number, since it uses as much as digits as its factorization.

16500721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 868478.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 16500721 is about 4062.1079503135. The cubic root of 16500721 is about 254.5858765854.

The spelling of 16500721 in words is "sixteen million, five hundred thousand, seven hundred twenty-one".