16818521 has 4 divisors (see below), whose sum is σ = 17398500. Its totient is φ = 16238544.

The previous prime is 16818517. The next prime is 16818533. The reversal of 16818521 is 12581861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12581861 = 367 ⋅34283.

It can be written as a sum of positive squares in 2 ways, for example, as 4840000 + 11978521 = 2200^2 + 3461^2 .

It is a cyclic number.

It is not a de Polignac number, because 16818521 - 2² = 16818517 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16818511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 289946 + ... + 290003.

It is an arithmetic number, because the mean of its divisors is an integer number (4349625).

Almost surely, 2^16818521 is an apocalyptic number.

It is an amenable number.

16818521 is a deficient number, since it is larger than the sum of its proper divisors (579979).

16818521 is an equidigital number, since it uses as much as digits as its factorization.

16818521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 579978.

The product of its digits is 3840, while the sum is 32.

The square root of 16818521 is about 4101.0390146888. The cubic root of 16818521 is about 256.2099159193.

The spelling of 16818521 in words is "sixteen million, eight hundred eighteen thousand, five hundred twenty-one".