645787680 has 96 divisors (see below), whose sum is σ = 2039494464. Its totient is φ = 171764736.

The previous prime is 645787657. The next prime is 645787699. The reversal of 645787680 is 86787546.

It is a tau number, because it is divible by the number of its divisors (96).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 211122 + ... + 214158.

It is an arithmetic number, because the mean of its divisors is an integer number (21244734).

Almost surely, 2^645787680 is an apocalyptic number.

645787680 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 645787680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1019747232).

645787680 is an abundant number, since it is smaller than the sum of its proper divisors (1393706784).

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

645787680 is a wasteful number, since it uses less digits than its factorization.

645787680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3498 (or 3490 counting only the distinct ones).

The product of its (nonzero) digits is 2257920, while the sum is 51.

The square root of 645787680 is about 25412.3529016894. The cubic root of 645787680 is about 864.3638299660.

The spelling of 645787680 in words is "six hundred forty-five million, seven hundred eighty-seven thousand, six hundred eighty".