81509108004 has 189 divisors, whose sum is σ = 227916641281. Its totient is φ = 25489261440.

The previous prime is 81509107991. The next prime is 81509108033. The reversal of 81509108004 is 40080190518.

The square root of 81509108004 is 285498.

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

It can be written as a sum of positive squares in only one way, i.e., 63458648100 + 18050459904 = 251910^2 + 134352^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81509108004.

It is an unprimeable number.

It is a polite number, since it can be written in 62 ways as a sum of consecutive naturals, for example, 262087009 + ... + 262087319.

Almost surely, 2^81509108004 is an apocalyptic number.

81509108004 is the 285498-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81509108004

81509108004 is an abundant number, since it is smaller than the sum of its proper divisors (146407533277).

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

81509108004 is an equidigital number, since it uses as much as digits as its factorization.

81509108004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 678 (or 333 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

Multiplying 81509108004 by its sum of digits (36), we get a square (2934327888144 = 1712988²).

81509108004 divided by its sum of digits (36) gives a square (2264141889 = 47583²).

The spelling of 81509108004 in words is "eighty-one billion, five hundred nine million, one hundred eight thousand, four".