66686261 has 2 divisors, whose sum is σ = 66686262. Its totient is φ = 66686260.

The previous prime is 66686251. The next prime is 66686287. The reversal of 66686261 is 16268666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 52200625 + 14485636 = 7225^2 + 3806^2 .

It is a cyclic number.

It is not a de Polignac number, because 66686261 - 2⁶ = 66686197 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66686201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33343130 + 33343131.

It is an arithmetic number, because the mean of its divisors is an integer number (33343131).

Almost surely, 2^66686261 is an apocalyptic number.

It is an amenable number.

66686261 is a deficient number, since it is larger than the sum of its proper divisors (1).

66686261 is an equidigital number, since it uses as much as digits as its factorization.

66686261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 41.

The square root of 66686261 is about 8166.1656240858. The cubic root of 66686261 is about 405.5198547113.

The spelling of 66686261 in words is "sixty-six million, six hundred eighty-six thousand, two hundred sixty-one".