645218136 has 160 divisors (see below), whose sum is σ = 1966472640. Its totient is φ = 196826112.

The previous prime is 645218117. The next prime is 645218137. The reversal of 645218136 is 631812546.

It is a happy number.

645218136 is a `hidden beast` number, since 645 + 2 + 1 + 8 + 1 + 3 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 645218136.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645218137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 406801 + ... + 408383.

It is an arithmetic number, because the mean of its divisors is an integer number (12290454).

Almost surely, 2^645218136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645218136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (983236320).

645218136 is an abundant number, since it is smaller than the sum of its proper divisors (1321254504).

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

645218136 is a wasteful number, since it uses less digits than its factorization.

645218136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1655 (or 1642 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 645218136 is about 25401.1443836690. The cubic root of 645218136 is about 864.1096504355.

The spelling of 645218136 in words is "six hundred forty-five million, two hundred eighteen thousand, one hundred thirty-six".