999993821 has 2 divisors, whose sum is σ = 999993822. Its totient is φ = 999993820.

The previous prime is 999993817. The next prime is 999993823. The reversal of 999993821 is 128399999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 587335225 + 412658596 = 24235^2 + 20314^2 .

It is a cyclic number.

It is not a de Polignac number, because 999993821 - 2² = 999993817 is a prime.

Together with 999993823, 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 (999993823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499996910 + 499996911.

It is an arithmetic number, because the mean of its divisors is an integer number (499996911).

Almost surely, 2^999993821 is an apocalyptic number.

It is an amenable number.

999993821 is a deficient number, since it is larger than the sum of its proper divisors (1).

999993821 is an equidigital number, since it uses as much as digits as its factorization.

999993821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2834352, while the sum is 59.

The square root of 999993821 is about 31622.6789029646. The cubic root of 999993821 is about 999.9979403291.

The spelling of 999993821 in words is "nine hundred ninety-nine million, nine hundred ninety-three thousand, eight hundred twenty-one".