821979 has 6 divisors (see below), whose sum is σ = 1187316. Its totient is φ = 547980.

The previous prime is 821971. The next prime is 821993. The reversal of 821979 is 979128.

It is a happy number.

It is not a de Polignac number, because 821979 - 2³ = 821971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (821971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 45657 + ... + 45674.

It is an arithmetic number, because the mean of its divisors is an integer number (197886).

2⁸²¹⁹⁷⁹ is an apocalyptic number.

821979 is a deficient number, since it is larger than the sum of its proper divisors (365337).

821979 is a wasteful number, since it uses less digits than its factorization.

821979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91337 (or 91334 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 821979 is about 906.6305752621. The cubic root of 821979 is about 93.6742534828.

The spelling of 821979 in words is "eight hundred twenty-one thousand, nine hundred seventy-nine".