6821491 has 2 divisors, whose sum is σ = 6821492. Its totient is φ = 6821490.

The previous prime is 6821473. The next prime is 6821497. The reversal of 6821491 is 1941286.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 6821491 - 2¹¹ = 6819443 is a prime.

It is not a weakly prime, because it can be changed into another prime (6821497) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3410745 + 3410746.

It is an arithmetic number, because the mean of its divisors is an integer number (3410746).

Almost surely, 2^6821491 is an apocalyptic number.

6821491 is a deficient number, since it is larger than the sum of its proper divisors (1).

6821491 is an equidigital number, since it uses as much as digits as its factorization.

6821491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 31.

The square root of 6821491 is about 2611.7984225434. The cubic root of 6821491 is about 189.6530232488.

The spelling of 6821491 in words is "six million, eight hundred twenty-one thousand, four hundred ninety-one".