16821491 has 2 divisors, whose sum is σ = 16821492. Its totient is φ = 16821490.

The previous prime is 16821481. The next prime is 16821529. The reversal of 16821491 is 19412861.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16821491 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16821401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8410745 + 8410746.

It is an arithmetic number, because the mean of its divisors is an integer number (8410746).

Almost surely, 2^16821491 is an apocalyptic number.

16821491 is a deficient number, since it is larger than the sum of its proper divisors (1).

16821491 is an equidigital number, since it uses as much as digits as its factorization.

16821491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 32.

The square root of 16821491 is about 4101.4011020626. The cubic root of 16821491 is about 256.2249964896.

The spelling of 16821491 in words is "sixteen million, eight hundred twenty-one thousand, four hundred ninety-one".