66781697 has 4 divisors (see below), whose sum is σ = 66823380. Its totient is φ = 66740016.

The previous prime is 66781681. The next prime is 66781699. The reversal of 66781697 is 79618766.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 32160241 + 34621456 = 5671^2 + 5884^2 .

It is a cyclic number.

It is not a de Polignac number, because 66781697 - 2⁴ = 66781681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66781699) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18338 + ... + 21675.

It is an arithmetic number, because the mean of its divisors is an integer number (16705845).

Almost surely, 2^66781697 is an apocalyptic number.

It is an amenable number.

66781697 is a deficient number, since it is larger than the sum of its proper divisors (41683).

66781697 is a wasteful number, since it uses less digits than its factorization.

66781697 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41682.

The product of its digits is 762048, while the sum is 50.

The square root of 66781697 is about 8172.0069138493. The cubic root of 66781697 is about 405.7132116084.

The spelling of 66781697 in words is "sixty-six million, seven hundred eighty-one thousand, six hundred ninety-seven".