645521536 has 64 divisors (see below), whose sum is σ = 1440941760. Its totient is φ = 285465600.

The previous prime is 645521431. The next prime is 645521543. The reversal of 645521536 is 635125546.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a junction number, because it is equal to n+sod(n) for n = 645521495 and 645521504.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45901 + ... + 58291.

It is an arithmetic number, because the mean of its divisors is an integer number (22514715).

Almost surely, 2^645521536 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 645521536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (720470880).

645521536 is an abundant number, since it is smaller than the sum of its proper divisors (795420224).

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

645521536 is a wasteful number, since it uses less digits than its factorization.

645521536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12453 (or 12441 counting only the distinct ones).

The product of its digits is 108000, while the sum is 37.

The square root of 645521536 is about 25407.1158536344. The cubic root of 645521536 is about 864.2450722258.

The spelling of 645521536 in words is "six hundred forty-five million, five hundred twenty-one thousand, five hundred thirty-six".