645272181 has 12 divisors (see below), whose sum is σ = 937449708. Its totient is φ = 427693824.

The previous prime is 645272137. The next prime is 645272189. The reversal of 645272181 is 181272546.

645272181 is a `hidden beast` number, since 645 + 2 + 7 + 2 + 1 + 8 + 1 = 666.

645272181 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 2 ways, for example, as 413471556 + 231800625 = 20334^2 + 15225^2 .

It is not a de Polignac number, because 645272181 - 2¹¹ = 645270133 is a prime.

It is a super-2 number, since 2×645272181² = 832752375144993522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645272189) 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, 205660 + ... + 208773.

It is an arithmetic number, because the mean of its divisors is an integer number (78120809).

Almost surely, 2^645272181 is an apocalyptic number.

It is an amenable number.

645272181 is a deficient number, since it is larger than the sum of its proper divisors (292177527).

645272181 is a wasteful number, since it uses less digits than its factorization.

645272181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 414612 (or 414609 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 645272181 is about 25402.2081914152. The cubic root of 645272181 is about 864.1337763859.

The spelling of 645272181 in words is "six hundred forty-five million, two hundred seventy-two thousand, one hundred eighty-one".