7257821 has 2 divisors, whose sum is σ = 7257822. Its totient is φ = 7257820.

The previous prime is 7257799. The next prime is 7257823. The reversal of 7257821 is 1287527.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5784025 + 1473796 = 2405^2 + 1214^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7257821 is a prime.

It is a Sophie Germain prime.

Together with 7257823, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7257823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3628910 + 3628911.

It is an arithmetic number, because the mean of its divisors is an integer number (3628911).

Almost surely, 2^7257821 is an apocalyptic number.

It is an amenable number.

7257821 is a deficient number, since it is larger than the sum of its proper divisors (1).

7257821 is an equidigital number, since it uses as much as digits as its factorization.

7257821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7840, while the sum is 32.

The square root of 7257821 is about 2694.0343353417. The cubic root of 7257821 is about 193.6134027132.

The spelling of 7257821 in words is "seven million, two hundred fifty-seven thousand, eight hundred twenty-one".