821721716 has 12 divisors (see below), whose sum is σ = 1441637988. Its totient is φ = 409825152.

The previous prime is 821721697. The next prime is 821721731. The reversal of 821721716 is 617127128.

It can be written as a sum of positive squares in 2 ways, for example, as 191711716 + 630010000 = 13846^2 + 25100^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 257141 + ... + 260316.

It is an arithmetic number, because the mean of its divisors is an integer number (120136499).

Almost surely, 2^821721716 is an apocalyptic number.

It is an amenable number.

821721716 is a deficient number, since it is larger than the sum of its proper divisors (619916272).

821721716 is a wasteful number, since it uses less digits than its factorization.

821721716 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 517858 (or 517856 counting only the distinct ones).

The product of its digits is 9408, while the sum is 35.

The square root of 821721716 is about 28665.6888282839. The cubic root of 821721716 is about 936.6447894205.

The spelling of 821721716 in words is "eight hundred twenty-one million, seven hundred twenty-one thousand, seven hundred sixteen".