8420521 has 2 divisors, whose sum is σ = 8420522. Its totient is φ = 8420520.

The previous prime is 8420519. The next prime is 8420543. The reversal of 8420521 is 1250248.

It is an a-pointer prime, because the next prime (8420543) can be obtained adding 8420521 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7398400 + 1022121 = 2720^2 + 1011^2 .

It is a cyclic number.

It is not a de Polignac number, because 8420521 - 2¹ = 8420519 is a prime.

It is a super-2 number, since 2×8420521² = 141810347822882, which contains 22 as substring.

Together with 8420519, it forms a pair of twin primes.

It is an Ulam number.

8420521 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 8420492 and 8420501.

It is not a weakly prime, because it can be changed into another prime (8420221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4210260 + 4210261.

It is an arithmetic number, because the mean of its divisors is an integer number (4210261).

Almost surely, 2^8420521 is an apocalyptic number.

It is an amenable number.

8420521 is a deficient number, since it is larger than the sum of its proper divisors (1).

8420521 is an equidigital number, since it uses as much as digits as its factorization.

8420521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 8420521 is about 2901.8133985493. The cubic root of 8420521 is about 203.4446722192. Note that the first 3 decimals are identical.

Adding to 8420521 its reverse (1250248), we get a palindrome (9670769).

The spelling of 8420521 in words is "eight million, four hundred twenty thousand, five hundred twenty-one".