820399366081 has 3 divisors (see below), whose sum is σ = 820400271841. Its totient is φ = 820398460322.

The previous prime is 820399366037. The next prime is 820399366093. The reversal of 820399366081 is 180663993028.

The square root of 820399366081 is 905759.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 820399366081 - 2¹¹ = 820399364033 is a prime.

It is a super-2 number, since 2×820399366081² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (820399366021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 452880 + ... + 1358638.

Almost surely, 2^820399366081 is an apocalyptic number.

820399366081 is the 905759-th square number.

820399366081 is the 452880-th centered octagonal number.

It is an amenable number.

820399366081 is a deficient number, since it is larger than the sum of its proper divisors (905760).

820399366081 is an frugal number, since it uses more digits than its factorization.

820399366081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1811518 (or 905759 counting only the distinct ones).

The product of its (nonzero) digits is 3359232, while the sum is 55.

The spelling of 820399366081 in words is "eight hundred twenty billion, three hundred ninety-nine million, three hundred sixty-six thousand, eighty-one".