8421521 has 4 divisors (see below), whose sum is σ = 8445732. Its totient is φ = 8397312.

The previous prime is 8421509. The next prime is 8421529. The reversal of 8421521 is 1251248.

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 1661521 + 6760000 = 1289^2 + 2600^2 .

It is a cyclic number.

It is not a de Polignac number, because 8421521 - 2¹⁸ = 8159377 is a prime.

It is a d-powerful number, because it can be written as 8⁵ + 4² + 2 + 1 + 5³ + 2²³ + 1 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8421529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11576 + ... + 12281.

It is an arithmetic number, because the mean of its divisors is an integer number (2111433).

Almost surely, 2^8421521 is an apocalyptic number.

It is an amenable number.

8421521 is a deficient number, since it is larger than the sum of its proper divisors (24211).

8421521 is a wasteful number, since it uses less digits than its factorization.

8421521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24210.

The product of its digits is 640, while the sum is 23.

The square root of 8421521 is about 2901.9856994823. The cubic root of 8421521 is about 203.4527254271.

Adding to 8421521 its reverse (1251248), we get a palindrome (9672769).

The spelling of 8421521 in words is "eight million, four hundred twenty-one thousand, five hundred twenty-one".