821969 has 4 divisors (see below), whose sum is σ = 829620. Its totient is φ = 814320.

The previous prime is 821941. The next prime is 821971. The reversal of 821969 is 969128.

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

It can be written as a sum of positive squares in 2 ways, for example, as 313600 + 508369 = 560^2 + 713^2 .

It is a cyclic number.

It is not a de Polignac number, because 821969 - 2¹⁶ = 756433 is a prime.

It is a super-2 number, since 2×821969² = 1351266073922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821939) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3662 + ... + 3879.

It is an arithmetic number, because the mean of its divisors is an integer number (207405).

2⁸²¹⁹⁶⁹ is an apocalyptic number.

It is an amenable number.

821969 is a deficient number, since it is larger than the sum of its proper divisors (7651).

821969 is a wasteful number, since it uses less digits than its factorization.

821969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7650.

The product of its digits is 7776, while the sum is 35.

The square root of 821969 is about 906.6250603199. The cubic root of 821969 is about 93.6738736084.

The spelling of 821969 in words is "eight hundred twenty-one thousand, nine hundred sixty-nine".