869821 has 4 divisors (see below), whose sum is σ = 882144. Its totient is φ = 857500.

The previous prime is 869819. The next prime is 869849. The reversal of 869821 is 128968.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a 4-Lehmer number, since φ(869821) divides (869821-1)⁴.

It is a cyclic number.

It is not a de Polignac number, because 869821 - 2¹ = 869819 is a prime.

It is a Duffinian number.

869821 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (869021) 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, 6055 + ... + 6196.

It is an arithmetic number, because the mean of its divisors is an integer number (220536).

2⁸⁶⁹⁸²¹ is an apocalyptic number.

It is an amenable number.

869821 is a deficient number, since it is larger than the sum of its proper divisors (12323).

869821 is a wasteful number, since it uses less digits than its factorization.

869821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12322.

The product of its digits is 6912, while the sum is 34.

The square root of 869821 is about 932.6419463009. The cubic root of 869821 is about 95.4574794948.

The spelling of 869821 in words is "eight hundred sixty-nine thousand, eight hundred twenty-one".