820819692081 has 9 divisors (see below), whose sum is σ = 1185632370091. Its totient is φ = 547211316072.

The previous prime is 820819692067. The next prime is 820819692101. The reversal of 820819692081 is 180296918028.

The square root of 820819692081 is 905991.

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

820819692081 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 98856792225 + 721962899856 = 314415^2 + 849684^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 820819692081 - 2⁷ = 820819691953 is a prime.

It is a super-2 number, since 2×820819692081² (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 (820819692061) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2566975 + ... + 2868971.

Almost surely, 2^820819692081 is an apocalyptic number.

820819692081 is the 905991-st square number.

820819692081 is the 452996-th centered octagonal number.

It is an amenable number.

820819692081 is a deficient number, since it is larger than the sum of its proper divisors (364812678010).

820819692081 is an frugal number, since it uses more digits than its factorization.

820819692081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 604000 (or 302000 counting only the distinct ones).

The product of its (nonzero) digits is 995328, while the sum is 54.

It can be divided in two parts, 820819 and 692081, that added together give a square (1512900 = 1230²).

The spelling of 820819692081 in words is "eight hundred twenty billion, eight hundred nineteen million, six hundred ninety-two thousand, eighty-one".