665533601280 has 640 divisors, whose sum is σ = 2427819609600. Its totient is φ = 172742049792.

The previous prime is 665533601267. The next prime is 665533601281. The reversal of 665533601280 is 82106335566.

665533601280 is a `hidden beast` number, since 6 + 6 + 5 + 5 + 3 + 360 + 1 + 280 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665533601281) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 509206387 + ... + 509207693.

It is an arithmetic number, because the mean of its divisors is an integer number (3793468140).

Almost surely, 2^665533601280 is an apocalyptic number.

665533601280 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 665533601280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1213909804800).

665533601280 is an abundant number, since it is smaller than the sum of its proper divisors (1762286008320).

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

665533601280 is a wasteful number, since it uses less digits than its factorization.

665533601280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1531 (or 1509 counting only the distinct ones).

The product of its (nonzero) digits is 777600, while the sum is 45.

The spelling of 665533601280 in words is "six hundred sixty-five billion, five hundred thirty-three million, six hundred one thousand, two hundred eighty".