66381355440 has 80 divisors (see below), whose sum is σ = 228646898400. Its totient is φ = 17701694208.

The previous prime is 66381355429. The next prime is 66381355441. The reversal of 66381355440 is 4455318366.

66381355440 is a `hidden beast` number, since 6 + 638 + 1 + 3 + 5 + 5 + 4 + 4 + 0 = 666.

66381355440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (80).

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

It is not an unprimeable number, because it can be changed into a prime (66381355441) 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, 15363895 + ... + 15368214.

It is an arithmetic number, because the mean of its divisors is an integer number (2858086230).

Almost surely, 2^66381355440 is an apocalyptic number.

66381355440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66381355440 is an abundant number, since it is smaller than the sum of its proper divisors (162265542960).

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

66381355440 is a wasteful number, since it uses less digits than its factorization.

66381355440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30732131 (or 30732119 counting only the distinct ones).

The product of its (nonzero) digits is 1036800, while the sum is 45.

It can be divided in two parts, 66381 and 355440, that added together give a triangular number (421821 = T₉₁₈).

The spelling of 66381355440 in words is "sixty-six billion, three hundred eighty-one million, three hundred fifty-five thousand, four hundred forty".