66765908881 has 9 divisors (see below), whose sum is σ = 77668569531. Its totient is φ = 57226371552.

The previous prime is 66765908831. The next prime is 66765908893. The reversal of 66765908881 is 18880956766.

The square root of 66765908881 is 258391.

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

It can be written as a sum of positive squares in only one way, i.e., 66411867025 + 354041856 = 257705^2 + 18816^2 .

It is not a de Polignac number, because 66765908881 - 2⁷ = 66765908753 is a prime.

It is a super-2 number, since 2×66765908881² (a number of 22 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66765908831) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1790281 + ... + 1827193.

It is an arithmetic number, because the mean of its divisors is an integer number (8629841059).

Almost surely, 2^66765908881 is an apocalyptic number.

66765908881 is the 258391-st square number.

66765908881 is the 129196-th centered octagonal number.

It is an amenable number.

66765908881 is a deficient number, since it is larger than the sum of its proper divisors (10902660650).

66765908881 is an frugal number, since it uses more digits than its factorization.

66765908881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73840 (or 36920 counting only the distinct ones).

The product of its (nonzero) digits is 34836480, while the sum is 64.

Multiplying 66765908881 by its sum of digits (64), we get a square (4273018168384 = 2067128²).

The spelling of 66765908881 in words is "sixty-six billion, seven hundred sixty-five million, nine hundred eight thousand, eight hundred eighty-one".