645660663840 has 384 divisors, whose sum is σ = 2296111587840. Its totient is φ = 169431552000.

The previous prime is 645660663797. The next prime is 645660663841. The reversal of 645660663840 is 48366066546.

It is a happy number.

645660663840 is a `hidden beast` number, since 6 + 4 + 566 + 0 + 6 + 6 + 38 + 40 = 666.

It is a super-3 number, since 3×645660663840³ (a number of 36 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (645660663841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 72861010 + ... + 72869870.

It is an arithmetic number, because the mean of its divisors is an integer number (5979457260).

Almost surely, 2^645660663840 is an apocalyptic number.

645660663840 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 645660663840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1148055793920).

645660663840 is an abundant number, since it is smaller than the sum of its proper divisors (1650450924000).

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

645660663840 is a wasteful number, since it uses less digits than its factorization.

645660663840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9153 (or 9139 counting only the distinct ones).

The product of its (nonzero) digits is 14929920, while the sum is 54.

The spelling of 645660663840 in words is "six hundred forty-five billion, six hundred sixty million, six hundred sixty-three thousand, eight hundred forty".