821640971 has 2 divisors, whose sum is σ = 821640972. Its totient is φ = 821640970.

The previous prime is 821640961. The next prime is 821641027. The reversal of 821640971 is 179046128.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 821640971 - 2¹⁸ = 821378827 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (821640901) 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, 410820485 + 410820486.

It is an arithmetic number, because the mean of its divisors is an integer number (410820486).

Almost surely, 2^821640971 is an apocalyptic number.

821640971 is a deficient number, since it is larger than the sum of its proper divisors (1).

821640971 is an equidigital number, since it uses as much as digits as its factorization.

821640971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 821640971 is about 28664.2804026196. The cubic root of 821640971 is about 936.6141091795.

The spelling of 821640971 in words is "eight hundred twenty-one million, six hundred forty thousand, nine hundred seventy-one".