645020181 has 24 divisors (see below), whose sum is σ = 1004372096. Its totient is φ = 396537120.

The previous prime is 645020153. The next prime is 645020183. The reversal of 645020181 is 181020546.

645020181 is a `hidden beast` number, since 6 + 450 + 201 + 8 + 1 = 666.

It is not a de Polignac number, because 645020181 - 2¹¹ = 645018133 is a prime.

It is a super-2 number, since 2×645020181² = 832102067794545522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (27) 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 (645020183) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 150336 + ... + 154566.

Almost surely, 2^645020181 is an apocalyptic number.

It is an amenable number.

645020181 is a deficient number, since it is larger than the sum of its proper divisors (359351915).

645020181 is a wasteful number, since it uses less digits than its factorization.

645020181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5553 (or 5550 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 645020181 is about 25397.2475083423. The cubic root of 645020181 is about 864.0212708562.

The spelling of 645020181 in words is "six hundred forty-five million, twenty thousand, one hundred eighty-one".