6999821 has 2 divisors, whose sum is σ = 6999822. Its totient is φ = 6999820.

The previous prime is 6999799. The next prime is 6999823. The reversal of 6999821 is 1289996.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5593225 + 1406596 = 2365^2 + 1186^2 .

It is a cyclic number.

It is not a de Polignac number, because 6999821 - 2¹⁴ = 6983437 is a prime.

Together with 6999823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6999823) 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, 3499910 + 3499911.

It is an arithmetic number, because the mean of its divisors is an integer number (3499911).

Almost surely, 2^6999821 is an apocalyptic number.

It is an amenable number.

6999821 is a deficient number, since it is larger than the sum of its proper divisors (1).

6999821 is an equidigital number, since it uses as much as digits as its factorization.

6999821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 44.

The square root of 6999821 is about 2645.7174830280. The cubic root of 6999821 is about 191.2914877172.

The spelling of 6999821 in words is "six million, nine hundred ninety-nine thousand, eight hundred twenty-one".