16691281 has 2 divisors, whose sum is σ = 16691282. Its totient is φ = 16691280.

The previous prime is 16691243. The next prime is 16691293. The reversal of 16691281 is 18219661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15872256 + 819025 = 3984^2 + 905^2 .

It is a cyclic number.

It is not a de Polignac number, because 16691281 - 2¹⁵ = 16658513 is a prime.

It is a super-2 number, since 2×16691281² = 557197722841922, which contains 22 as substring.

It is equal to p_1072699 and since 16691281 and 1072699 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 (16691221) 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 as a sum of consecutive naturals, namely, 8345640 + 8345641.

It is an arithmetic number, because the mean of its divisors is an integer number (8345641).

Almost surely, 2^16691281 is an apocalyptic number.

It is an amenable number.

16691281 is a deficient number, since it is larger than the sum of its proper divisors (1).

16691281 is an equidigital number, since it uses as much as digits as its factorization.

16691281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 34.

The square root of 16691281 is about 4085.4964202652. The cubic root of 16691281 is about 255.5621635832.

The spelling of 16691281 in words is "sixteen million, six hundred ninety-one thousand, two hundred eighty-one".