645470640 has 160 divisors (see below), whose sum is σ = 2239142400. Its totient is φ = 170899200.

The previous prime is 645470627. The next prime is 645470647. The reversal of 645470640 is 46074546.

645470640 is a `hidden beast` number, since 6 + 4 + 5 + 4 + 7 + 0 + 640 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 645470595 and 645470604.

It is not an unprimeable number, because it can be changed into a prime (645470647) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 325171 + ... + 327149.

It is an arithmetic number, because the mean of its divisors is an integer number (13994640).

Almost surely, 2^645470640 is an apocalyptic number.

645470640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645470640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1119571200).

645470640 is an abundant number, since it is smaller than the sum of its proper divisors (1593671760).

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

645470640 is a wasteful number, since it uses less digits than its factorization.

645470640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2152 (or 2140 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 36.

The square root of 645470640 is about 25406.1142247294. The cubic root of 645470640 is about 864.2223578928. Note that the first 3 decimals are identical.

The spelling of 645470640 in words is "six hundred forty-five million, four hundred seventy thousand, six hundred forty".