821315939 has 4 divisors (see below), whose sum is σ = 825571656. Its totient is φ = 817060224.

The previous prime is 821315933. The next prime is 821315969. The reversal of 821315939 is 939513128.

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

It is a cyclic number.

It is not a de Polignac number, because 821315939 - 2²⁰ = 820267363 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 821315896 and 821315905.

It is not an unprimeable number, because it can be changed into a prime (821315933) 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, 2127569 + ... + 2127954.

It is an arithmetic number, because the mean of its divisors is an integer number (206392914).

Almost surely, 2^821315939 is an apocalyptic number.

821315939 is a deficient number, since it is larger than the sum of its proper divisors (4255717).

821315939 is a wasteful number, since it uses less digits than its factorization.

821315939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4255716.

The product of its digits is 58320, while the sum is 41.

The square root of 821315939 is about 28658.6102070564. The cubic root of 821315939 is about 936.4905881934.

The spelling of 821315939 in words is "eight hundred twenty-one million, three hundred fifteen thousand, nine hundred thirty-nine".