821640986 has 4 divisors (see below), whose sum is σ = 1232461482. Its totient is φ = 410820492.

The previous prime is 821640971. The next prime is 821641027. The reversal of 821640986 is 689046128.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 603635761 + 218005225 = 24569^2 + 14765^2 .

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 as a sum of consecutive naturals, namely, 205410245 + ... + 205410248.

Almost surely, 2^821640986 is an apocalyptic number.

821640986 is a deficient number, since it is larger than the sum of its proper divisors (410820496).

821640986 is a wasteful number, since it uses less digits than its factorization.

821640986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 410820495.

The product of its (nonzero) digits is 165888, while the sum is 44.

The square root of 821640986 is about 28664.2806642693. The cubic root of 821640986 is about 936.6141148791.

The spelling of 821640986 in words is "eight hundred twenty-one million, six hundred forty thousand, nine hundred eighty-six".