66509831025 has 135 divisors (see below), whose sum is σ = 135677717329. Its totient is φ = 32185296000.

The previous prime is 66509830997. The next prime is 66509831053. The reversal of 66509831025 is 52013890566.

The square root of 66509831025 is 257895.

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

66509831025 is a `hidden beast` number, since 66 + 509 + 83 + 1 + 0 + 2 + 5 = 666.

It is an interprime number because it is at equal distance from previous prime (66509830997) and next prime (66509831053).

It can be written as a sum of positive squares in 4 ways, for example, as 8349756129 + 58160074896 = 91377^2 + 241164^2 .

It is a tau number, because it is divible by the number of its divisors (135).

It is not a de Polignac number, because 66509831025 - 2⁷ = 66509830897 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

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 134 ways as a sum of consecutive naturals, for example, 127657765 + ... + 127658285.

Almost surely, 2^66509831025 is an apocalyptic number.

66509831025 is the 257895-th square number.

66509831025 is the 128948-th centered octagonal number.

It is an amenable number.

66509831025 is an abundant number, since it is smaller than the sum of its proper divisors (69167886304).

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

66509831025 is an equidigital number, since it uses as much as digits as its factorization.

66509831025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1086 (or 540 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 45.

The spelling of 66509831025 in words is "sixty-six billion, five hundred nine million, eight hundred thirty-one thousand, twenty-five".