820893991 has 2 divisors, whose sum is σ = 820893992. Its totient is φ = 820893990.

The previous prime is 820893967. The next prime is 820894003. The reversal of 820893991 is 199398028.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 820893991 - 2¹⁹ = 820369703 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820893911) 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, 410446995 + 410446996.

It is an arithmetic number, because the mean of its divisors is an integer number (410446996).

Almost surely, 2^820893991 is an apocalyptic number.

820893991 is a deficient number, since it is larger than the sum of its proper divisors (1).

820893991 is an equidigital number, since it uses as much as digits as its factorization.

820893991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 279936, while the sum is 49.

The square root of 820893991 is about 28651.2476342654. The cubic root of 820893991 is about 936.3301878731.

The spelling of 820893991 in words is "eight hundred twenty million, eight hundred ninety-three thousand, nine hundred ninety-one".