821640985 has 16 divisors (see below), whose sum is σ = 1079128512. Its totient is φ = 595598400.

The previous prime is 821640971. The next prime is 821641027. The reversal of 821640985 is 589046128.

It is a happy number.

It is not a de Polignac number, because 821640985 - 2⁷ = 821640857 is a prime.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 7446 + ... + 41215.

It is an arithmetic number, because the mean of its divisors is an integer number (67445532).

Almost surely, 2^821640985 is an apocalyptic number.

It is an amenable number.

821640985 is a deficient number, since it is larger than the sum of its proper divisors (257487527).

821640985 is a wasteful number, since it uses less digits than its factorization.

821640985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48984.

The product of its (nonzero) digits is 138240, while the sum is 43.

The square root of 821640985 is about 28664.2806468259. The cubic root of 821640985 is about 936.6141144992.

The spelling of 821640985 in words is "eight hundred twenty-one million, six hundred forty thousand, nine hundred eighty-five".