8181421 has 2 divisors, whose sum is σ = 8181422. Its totient is φ = 8181420.

The previous prime is 8181389. The next prime is 8181449. The reversal of 8181421 is 1241818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7209225 + 972196 = 2685^2 + 986^2 .

It is a cyclic number.

It is not a de Polignac number, because 8181421 - 2⁵ = 8181389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8181221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4090710 + 4090711.

It is an arithmetic number, because the mean of its divisors is an integer number (4090711).

Almost surely, 2^8181421 is an apocalyptic number.

It is an amenable number.

8181421 is a deficient number, since it is larger than the sum of its proper divisors (1).

8181421 is an equidigital number, since it uses as much as digits as its factorization.

8181421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 512, while the sum is 25.

The square root of 8181421 is about 2860.3183389266. The cubic root of 8181421 is about 201.5005551812.

The spelling of 8181421 in words is "eight million, one hundred eighty-one thousand, four hundred twenty-one".