645704257664 has 128 divisors (see below), whose sum is σ = 1381168454400. Its totient is φ = 299602427904.

The previous prime is 645704257663. The next prime is 645704257697. The reversal of 645704257664 is 466752407546.

It is a tau number, because it is divible by the number of its divisors (128).

It is not an unprimeable number, because it can be changed into a prime (645704257663) 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, 150757667 + ... + 150761949.

It is an arithmetic number, because the mean of its divisors is an integer number (10790378550).

Almost surely, 2^645704257664 is an apocalyptic number.

645704257664 is a gapful number since it is divisible by the number (64) 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 645704257664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (690584227200).

645704257664 is an abundant number, since it is smaller than the sum of its proper divisors (735464196736).

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

645704257664 is a wasteful number, since it uses less digits than its factorization.

645704257664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5270 (or 5258 counting only the distinct ones).

The product of its (nonzero) digits is 33868800, while the sum is 56.

It can be divided in two parts, 64570 and 4257664, that added together give a palindrome (4322234).

The spelling of 645704257664 in words is "six hundred forty-five billion, seven hundred four million, two hundred fifty-seven thousand, six hundred sixty-four".