645418181 has 2 divisors, whose sum is σ = 645418182. Its totient is φ = 645418180.

The previous prime is 645418177. The next prime is 645418199. The reversal of 645418181 is 181814546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 620508100 + 24910081 = 24910^2 + 4991^2 .

It is a cyclic number.

It is not a de Polignac number, because 645418181 - 2² = 645418177 is a prime.

It is a super-2 number, since 2×645418181² = 833129256730697522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645412181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322709090 + 322709091.

It is an arithmetic number, because the mean of its divisors is an integer number (322709091).

Almost surely, 2^645418181 is an apocalyptic number.

It is an amenable number.

645418181 is a deficient number, since it is larger than the sum of its proper divisors (1).

645418181 is an equidigital number, since it uses as much as digits as its factorization.

645418181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30720, while the sum is 38.

The square root of 645418181 is about 25405.0817947906. The cubic root of 645418181 is about 864.1989447603.

The spelling of 645418181 in words is "six hundred forty-five million, four hundred eighteen thousand, one hundred eighty-one".