7821397 has 2 divisors, whose sum is σ = 7821398. Its totient is φ = 7821396.

The previous prime is 7821383. The next prime is 7821413. The reversal of 7821397 is 7931287.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4866436 + 2954961 = 2206^2 + 1719^2 .

It is a cyclic number.

It is not a de Polignac number, because 7821397 - 2¹⁹ = 7297109 is a prime.

It is a super-2 number, since 2×7821397² = 122348502063218, which contains 22 as substring.

It is a d-powerful number, because it can be written as 7⁶ + 8⁷ + 2 + 1 + 3¹⁴ + 9² + 7⁷ .

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7821367) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3910698 + 3910699.

It is an arithmetic number, because the mean of its divisors is an integer number (3910699).

Almost surely, 2^7821397 is an apocalyptic number.

It is an amenable number.

7821397 is a deficient number, since it is larger than the sum of its proper divisors (1).

7821397 is an equidigital number, since it uses as much as digits as its factorization.

7821397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21168, while the sum is 37.

The square root of 7821397 is about 2796.6760627574. The cubic root of 7821397 is about 198.5004261592.

The spelling of 7821397 in words is "seven million, eight hundred twenty-one thousand, three hundred ninety-seven".