8221521 has 16 divisors (see below), whose sum is σ = 13667328. Its totient is φ = 4270800.

The previous prime is 8221513. The next prime is 8221537. The reversal of 8221521 is 1251228.

It is a happy number.

It is not a de Polignac number, because 8221521 - 2³ = 8221513 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8221561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17565 + ... + 18026.

It is an arithmetic number, because the mean of its divisors is an integer number (854208).

Almost surely, 2^8221521 is an apocalyptic number.

It is an amenable number.

8221521 is a deficient number, since it is larger than the sum of its proper divisors (5445807).

8221521 is a wasteful number, since it uses less digits than its factorization.

8221521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35612.

The product of its digits is 320, while the sum is 21.

The square root of 8221521 is about 2867.3194799324. The cubic root of 8221521 is about 201.8292269707.

Adding to 8221521 its reverse (1251228), we get a palindrome (9472749).

The spelling of 8221521 in words is "eight million, two hundred twenty-one thousand, five hundred twenty-one".