821864 has 16 divisors (see below), whose sum is σ = 1622400. Its totient is φ = 389232.

The previous prime is 821861. The next prime is 821869. The reversal of 821864 is 468128.

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (821861) 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, 2552 + ... + 2855.

It is an arithmetic number, because the mean of its divisors is an integer number (101400).

2⁸²¹⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

821864 is a deficient number, since it is larger than the sum of its proper divisors (800536).

821864 is a wasteful number, since it uses less digits than its factorization.

821864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5432 (or 5428 counting only the distinct ones).

The product of its digits is 3072, while the sum is 29.

The square root of 821864 is about 906.5671514014. The cubic root of 821864 is about 93.6698847412.

The spelling of 821864 in words is "eight hundred twenty-one thousand, eight hundred sixty-four".