645123136 has 112 divisors (see below), whose sum is σ = 1541166336. Its totient is φ = 261955584.

The previous prime is 645123107. The next prime is 645123137. The reversal of 645123136 is 631321546.

It is a tau number, because it is divible by the number of its divisors (112).

It is a junction number, because it is equal to n+sod(n) for n = 645123098 and 645123107.

It is not an unprimeable number, because it can be changed into a prime (645123137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1411420 + ... + 1411876.

Almost surely, 2^645123136 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 645123136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (770583168).

645123136 is an abundant number, since it is smaller than the sum of its proper divisors (896043200).

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

645123136 is a wasteful number, since it uses less digits than its factorization.

645123136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636 (or 626 counting only the distinct ones).

The product of its digits is 12960, while the sum is 31.

The square root of 645123136 is about 25399.2743203423. The cubic root of 645123136 is about 864.0672387086.

The spelling of 645123136 in words is "six hundred forty-five million, one hundred twenty-three thousand, one hundred thirty-six".