66794851809 has 81 divisors (see below), whose sum is σ = 116263604691. Its totient is φ = 36844204320.

The previous prime is 66794851801. The next prime is 66794851811. The reversal of 66794851809 is 90815849766.

The square root of 66794851809 is 258447.

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

66794851809 is a `hidden beast` number, since 6 + 6 + 79 + 48 + 518 + 0 + 9 = 666.

66794851809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 44763980625 + 22030871184 = 211575^2 + 148428^2 .

It is not a de Polignac number, because 66794851809 - 2³ = 66794851801 is a prime.

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 (66794851801) 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, 168248799 + ... + 168249195.

Almost surely, 2^66794851809 is an apocalyptic number.

66794851809 is the 258447-th square number.

66794851809 is the 129224-th centered octagonal number.

It is an amenable number.

66794851809 is a deficient number, since it is larger than the sum of its proper divisors (49468752882).

66794851809 is an equidigital number, since it uses as much as digits as its factorization.

66794851809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 876 (or 438 counting only the distinct ones).

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

The spelling of 66794851809 in words is "sixty-six billion, seven hundred ninety-four million, eight hundred fifty-one thousand, eight hundred nine".