821388947 has 4 divisors (see below), whose sum is σ = 827298360. Its totient is φ = 815479536.

The previous prime is 821388923. The next prime is 821388959. The reversal of 821388947 is 749883128.

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 821388947 - 2⁸ = 821388691 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 821388895 and 821388904.

It is not an unprimeable number, because it can be changed into a prime (821385947) 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, 2954498 + ... + 2954775.

It is an arithmetic number, because the mean of its divisors is an integer number (206824590).

Almost surely, 2^821388947 is an apocalyptic number.

821388947 is a deficient number, since it is larger than the sum of its proper divisors (5909413).

821388947 is a wasteful number, since it uses less digits than its factorization.

821388947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5909412.

The product of its digits is 774144, while the sum is 50.

The square root of 821388947 is about 28659.8839320748. The cubic root of 821388947 is about 936.5183360534.

The spelling of 821388947 in words is "eight hundred twenty-one million, three hundred eighty-eight thousand, nine hundred forty-seven".