821142721 has 8 divisors (see below), whose sum is σ = 993651840. Its totient is φ = 662434368.

The previous prime is 821142719. The next prime is 821142731. The reversal of 821142721 is 127241128.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 821142721 - 2¹ = 821142719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 821142721.

It is not an unprimeable number, because it can be changed into a prime (821142701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3450061 + ... + 3450298.

It is an arithmetic number, because the mean of its divisors is an integer number (124206480).

Almost surely, 2^821142721 is an apocalyptic number.

It is an amenable number.

821142721 is a deficient number, since it is larger than the sum of its proper divisors (172509119).

821142721 is a wasteful number, since it uses less digits than its factorization.

821142721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6900383.

The product of its digits is 1792, while the sum is 28.

The square root of 821142721 is about 28655.5879541844. The cubic root of 821142721 is about 936.4247473379.

Adding to 821142721 its reverse (127241128), we get a palindrome (948383849).

The spelling of 821142721 in words is "eight hundred twenty-one million, one hundred forty-two thousand, seven hundred twenty-one".