16643491 has 4 divisors (see below), whose sum is σ = 16716400. Its totient is φ = 16570584.

The previous prime is 16643479. The next prime is 16643503. The reversal of 16643491 is 19434661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19434661 = 61 ⋅318601.

It is an interprime number because it is at equal distance from previous prime (16643479) and next prime (16643503).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16643491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16643401) 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, 36111 + ... + 36568.

It is an arithmetic number, because the mean of its divisors is an integer number (4179100).

Almost surely, 2^16643491 is an apocalyptic number.

16643491 is a deficient number, since it is larger than the sum of its proper divisors (72909).

16643491 is an equidigital number, since it uses as much as digits as its factorization.

16643491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72908.

The product of its digits is 15552, while the sum is 34.

The square root of 16643491 is about 4079.6434893260. The cubic root of 16643491 is about 255.3180243298.

The spelling of 16643491 in words is "sixteen million, six hundred forty-three thousand, four hundred ninety-one".