821326721 has 4 divisors (see below), whose sum is σ = 821589552. Its totient is φ = 821063892.

The previous prime is 821326717. The next prime is 821326769. The reversal of 821326721 is 127623128.

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 cyclic number.

It is not a de Polignac number, because 821326721 - 2² = 821326717 is a prime.

It is a super-2 number, since 2×821326721² = 1349155165257223682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821326771) 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, 126671 + ... + 132996.

It is an arithmetic number, because the mean of its divisors is an integer number (205397388).

Almost surely, 2^821326721 is an apocalyptic number.

It is an amenable number.

821326721 is a deficient number, since it is larger than the sum of its proper divisors (262831).

821326721 is a wasteful number, since it uses less digits than its factorization.

821326721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262830.

The product of its digits is 8064, while the sum is 32.

The square root of 821326721 is about 28658.7983174452. The cubic root of 821326721 is about 936.4946861687.

Adding to 821326721 its reverse (127623128), we get a palindrome (948949849).

The spelling of 821326721 in words is "eight hundred twenty-one million, three hundred twenty-six thousand, seven hundred twenty-one".