645781580 has 48 divisors (see below), whose sum is σ = 1418425344. Its totient is φ = 246502080.

The previous prime is 645781571. The next prime is 645781589. The reversal of 645781580 is 85187546.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (645781571) and next prime (645781589).

It is a super-3 number, since 3×645781580³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (645781589) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 229985 + ... + 232775.

It is an arithmetic number, because the mean of its divisors is an integer number (29550528).

Almost surely, 2^645781580 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 645781580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (709212672).

645781580 is an abundant number, since it is smaller than the sum of its proper divisors (772643764).

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

645781580 is a wasteful number, since it uses less digits than its factorization.

645781580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3326 (or 3324 counting only the distinct ones).

The product of its (nonzero) digits is 268800, while the sum is 44.

The square root of 645781580 is about 25412.2328810359. The cubic root of 645781580 is about 864.3611084132.

The spelling of 645781580 in words is "six hundred forty-five million, seven hundred eighty-one thousand, five hundred eighty".