8157421 has 2 divisors, whose sum is σ = 8157422. Its totient is φ = 8157420.

The previous prime is 8157379. The next prime is 8157431. The reversal of 8157421 is 1247518.

8157421 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7784100 + 373321 = 2790^2 + 611^2 .

It is a cyclic number.

It is not a de Polignac number, because 8157421 - 2⁷ = 8157293 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 8157421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8157431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4078710 + 4078711.

It is an arithmetic number, because the mean of its divisors is an integer number (4078711).

Almost surely, 2^8157421 is an apocalyptic number.

It is an amenable number.

8157421 is a deficient number, since it is larger than the sum of its proper divisors (1).

8157421 is an equidigital number, since it uses as much as digits as its factorization.

8157421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2240, while the sum is 28.

The square root of 8157421 is about 2856.1199204515. The cubic root of 8157421 is about 201.3033298735.

Subtracting from 8157421 its reverse (1247518), we obtain a triangular number (6909903 = T₃₇₁₇).

The spelling of 8157421 in words is "eight million, one hundred fifty-seven thousand, four hundred twenty-one".