16821493 has 4 divisors (see below), whose sum is σ = 18115468. Its totient is φ = 15527520.

The previous prime is 16821491. The next prime is 16821529. The reversal of 16821493 is 39412861.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2022084 + 14799409 = 1422^2 + 3847^2 .

It is a cyclic number.

It is not a de Polignac number, because 16821493 - 2¹ = 16821491 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16821491) 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 in 3 ways as a sum of consecutive naturals, for example, 646968 + ... + 646993.

It is an arithmetic number, because the mean of its divisors is an integer number (4528867).

Almost surely, 2^16821493 is an apocalyptic number.

16821493 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

16821493 is a deficient number, since it is larger than the sum of its proper divisors (1293975).

16821493 is a wasteful number, since it uses less digits than its factorization.

16821493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1293974.

The product of its digits is 10368, while the sum is 34.

The square root of 16821493 is about 4101.4013458817. The cubic root of 16821493 is about 256.2250066442.

The spelling of 16821493 in words is "sixteen million, eight hundred twenty-one thousand, four hundred ninety-three".