821865521 has 8 divisors (see below), whose sum is σ = 850752000. Its totient is φ = 793127520.

The previous prime is 821865491. The next prime is 821865523. The reversal of 821865521 is 125568128.

821865521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 821865521 - 2¹⁴ = 821849137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821865523) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25796 + ... + 48053.

It is an arithmetic number, because the mean of its divisors is an integer number (106344000).

Almost surely, 2^821865521 is an apocalyptic number.

It is an amenable number.

821865521 is a deficient number, since it is larger than the sum of its proper divisors (28886479).

821865521 is a wasteful number, since it uses less digits than its factorization.

821865521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74239.

The product of its digits is 38400, while the sum is 38.

The square root of 821865521 is about 28668.1970308563. The cubic root of 821865521 is about 936.6994252519.

The spelling of 821865521 in words is "eight hundred twenty-one million, eight hundred sixty-five thousand, five hundred twenty-one".