16510721 has 2 divisors, whose sum is σ = 16510722. Its totient is φ = 16510720.

The previous prime is 16510699. The next prime is 16510727. The reversal of 16510721 is 12701561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14440000 + 2070721 = 3800^2 + 1439^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16510721 is a prime.

It is equal to p_1061843 and since 16510721 and 1061843 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (16510727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8255360 + 8255361.

It is an arithmetic number, because the mean of its divisors is an integer number (8255361).

Almost surely, 2^16510721 is an apocalyptic number.

It is an amenable number.

16510721 is a deficient number, since it is larger than the sum of its proper divisors (1).

16510721 is an equidigital number, since it uses as much as digits as its factorization.

16510721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 16510721 is about 4063.3386518970. The cubic root of 16510721 is about 254.6372954425.

The spelling of 16510721 in words is "sixteen million, five hundred ten thousand, seven hundred twenty-one".