665505166225 has 27 divisors (see below), whose sum is σ = 829890623091. Its totient is φ = 529411833600.

The previous prime is 665505166217. The next prime is 665505166237. The reversal of 665505166225 is 522661505566.

The square root of 665505166225 is 815785.

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

It can be written as a sum of positive squares in 13 ways, for example, as 1371443089 + 664133723136 = 37033^2 + 814944^2 .

It is not a de Polignac number, because 665505166225 - 2³ = 665505166217 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 983020587 + ... + 983021263.

Almost surely, 2^665505166225 is an apocalyptic number.

665505166225 is the 815785-th square number.

665505166225 is the 407893-rd centered octagonal number.

It is an amenable number.

665505166225 is a deficient number, since it is larger than the sum of its proper divisors (164385456866).

665505166225 is an frugal number, since it uses more digits than its factorization.

665505166225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1846 (or 923 counting only the distinct ones).

The product of its (nonzero) digits is 3240000, while the sum is 49.

Multiplying 665505166225 by its sum of digits (49), we get a square (32609753145025 = 5710495²).

It can be divided in two parts, 6655051 and 66225, that added together give a palindrome (6721276).

The spelling of 665505166225 in words is "six hundred sixty-five billion, five hundred five million, one hundred sixty-six thousand, two hundred twenty-five".