818521 has 4 divisors (see below), whose sum is σ = 892944. Its totient is φ = 744100.

The previous prime is 818509. The next prime is 818561. The reversal of 818521 is 125818.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 818521 - 2⁷ = 818393 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (818561) 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, 37195 + ... + 37216.

It is an arithmetic number, because the mean of its divisors is an integer number (223236).

2⁸¹⁸⁵²¹ is an apocalyptic number.

It is an amenable number.

818521 is a deficient number, since it is larger than the sum of its proper divisors (74423).

818521 is a wasteful number, since it uses less digits than its factorization.

818521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74422.

The product of its digits is 640, while the sum is 25.

The square root of 818521 is about 904.7215041105. The cubic root of 818521 is about 93.5427088098.

The spelling of 818521 in words is "eight hundred eighteen thousand, five hundred twenty-one".