66756923181081 has 81 divisors (see below), whose sum is σ = 112728109160511. Its totient is φ = 37957878812448.

The previous prime is 66756923181071. The next prime is 66756923181103. The reversal of 66756923181081 is 18018132965766.

The square root of 66756923181081 is 8170491.

It is a perfect power (a square), and thus also a powerful number.

66756923181081 is a `hidden beast` number, since 6 + 67 + 569 + 2 + 3 + 1 + 8 + 1 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 62174155433481 + 4582767747600 = 7885059^2 + 2140740^2 .

It is not a de Polignac number, because 66756923181081 - 2¹⁷ = 66756923050009 is a prime.

It is a super-2 number, since 2×66756923181081² (a number of 28 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is not an unprimeable number, because it can be changed into a prime (66756923181071) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 39291890370 + ... + 39291892068.

Almost surely, 2^{66756923181081} is an apocalyptic number.

66756923181081 is the 8170491-st square number.

66756923181081 is the 4085246-th centered octagonal number.

It is an amenable number.

66756923181081 is a deficient number, since it is larger than the sum of its proper divisors (45971185979430).

66756923181081 is an frugal number, since it uses more digits than its factorization.

66756923181081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3876 (or 1938 counting only the distinct ones).

The product of its (nonzero) digits is 26127360, while the sum is 63.

The spelling of 66756923181081 in words is "sixty-six trillion, seven hundred fifty-six billion, nine hundred twenty-three million, one hundred eighty-one thousand, eighty-one".