645065781880 has 128 divisors (see below), whose sum is σ = 1588026384000. Its totient is φ = 234386030592.

The previous prime is 645065781853. The next prime is 645065781907. The reversal of 645065781880 is 88187560546.

It is an interprime number because it is at equal distance from previous prime (645065781853) and next prime (645065781907).

It is a super-2 number, since 2×645065781880² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17025117 + ... + 17062963.

It is an arithmetic number, because the mean of its divisors is an integer number (12406456125).

Almost surely, 2^645065781880 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 645065781880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (794013192000).

645065781880 is an abundant number, since it is smaller than the sum of its proper divisors (942960602120).

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

645065781880 is a wasteful number, since it uses less digits than its factorization.

645065781880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38393 (or 38389 counting only the distinct ones).

The product of its (nonzero) digits is 12902400, while the sum is 58.

The spelling of 645065781880 in words is "six hundred forty-five billion, sixty-five million, seven hundred eighty-one thousand, eight hundred eighty".