81820215173124 has 36 divisors (see below), whose sum is σ = 206823807892156. Its totient is φ = 27273340942848.

The previous prime is 81820215173119. The next prime is 81820215173129. The reversal of 81820215173124 is 42137151202818.

81820215173124 is a `hidden beast` number, since 8 + 1 + 8 + 2 + 0 + 2 + 1 + 517 + 3 + 124 = 666.

It is an interprime number because it is at equal distance from previous prime (81820215173119) and next prime (81820215173129).

It can be written as a sum of positive squares in 2 ways, for example, as 22604604624900 + 59215610548224 = 4754430^2 + 7695168^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×81820215173124² (a number of 29 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81820215173124.

It is not an unprimeable number, because it can be changed into a prime (81820215173129) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14338752 + ... + 19215624.

Almost surely, 2^{81820215173124} is an apocalyptic number.

It is an amenable number.

81820215173124 is an abundant number, since it is smaller than the sum of its proper divisors (125003592719032).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81820215173124 is a wasteful number, since it uses less digits than its factorization.

81820215173124 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5342916 (or 5342911 counting only the distinct ones).

The product of its (nonzero) digits is 215040, while the sum is 45.

The spelling of 81820215173124 in words is "eighty-one trillion, eight hundred twenty billion, two hundred fifteen million, one hundred seventy-three thousand, one hundred twenty-four".