66611561760 has 480 divisors, whose sum is σ = 246086173872. Its totient is φ = 16950435840.

The previous prime is 66611561747. The next prime is 66611561773. The reversal of 66611561760 is 6716511666.

It is an interprime number because it is at equal distance from previous prime (66611561747) and next prime (66611561773).

It can be written as a sum of positive squares in 8 ways, for example, as 59276667024 + 7334894736 = 243468^2 + 85644^2 .

It is a tau number, because it is divible by the number of its divisors (480).

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

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 25413250 + ... + 25415870.

Almost surely, 2^66611561760 is an apocalyptic number.

66611561760 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 66611561760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (123043086936).

66611561760 is an abundant number, since it is smaller than the sum of its proper divisors (179474612112).

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

66611561760 is a wasteful number, since it uses less digits than its factorization.

66611561760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2738 (or 2721 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The spelling of 66611561760 in words is "sixty-six billion, six hundred eleven million, five hundred sixty-one thousand, seven hundred sixty".