645319640 has 64 divisors (see below), whose sum is σ = 1670492160. Its totient is φ = 219772800.

The previous prime is 645319559. The next prime is 645319663. The reversal of 645319640 is 46913546.

It is a hoax number, since the sum of its digits (38) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 645319594 and 645319603.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 34649 + ... + 49911.

It is an arithmetic number, because the mean of its divisors is an integer number (26101440).

Almost surely, 2^645319640 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 645319640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (835246080).

645319640 is an abundant number, since it is smaller than the sum of its proper divisors (1025172520).

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

645319640 is a wasteful number, since it uses less digits than its factorization.

645319640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15432 (or 15428 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 38.

The square root of 645319640 is about 25403.1423253109. The cubic root of 645319640 is about 864.1549612030.

The spelling of 645319640 in words is "six hundred forty-five million, three hundred nineteen thousand, six hundred forty".