645544040 has 16 divisors (see below), whose sum is σ = 1452474180. Its totient is φ = 258217600.

The previous prime is 645544007. The next prime is 645544051. The reversal of 645544040 is 40445546.

It can be written as a sum of positive squares in 2 ways, for example, as 586899076 + 58644964 = 24226^2 + 7658^2 .

It is a junction number, because it is equal to n+sod(n) for n = 645543988 and 645544006.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8069261 + ... + 8069340.

Almost surely, 2^645544040 is an apocalyptic number.

It is an amenable number.

645544040 is an abundant number, since it is smaller than the sum of its proper divisors (806930140).

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

645544040 is a wasteful number, since it uses less digits than its factorization.

645544040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16138612 (or 16138608 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 32.

The square root of 645544040 is about 25407.5587178304. The cubic root of 645544040 is about 864.2551151363.

Adding to 645544040 its reverse (40445546), we get a palindrome (685989586).

The spelling of 645544040 in words is "six hundred forty-five million, five hundred forty-four thousand, forty".