66761221 has 2 divisors, whose sum is σ = 66761222. Its totient is φ = 66761220.

The previous prime is 66761183. The next prime is 66761237. The reversal of 66761221 is 12216766.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66748900 + 12321 = 8170^2 + 111^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66761221 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 (66761621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33380610 + 33380611.

It is an arithmetic number, because the mean of its divisors is an integer number (33380611).

Almost surely, 2^66761221 is an apocalyptic number.

It is an amenable number.

66761221 is a deficient number, since it is larger than the sum of its proper divisors (1).

66761221 is an equidigital number, since it uses as much as digits as its factorization.

66761221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 31.

The square root of 66761221 is about 8170.7540043744. The cubic root of 66761221 is about 405.6717419978.

Adding to 66761221 its reverse (12216766), we get a palindrome (78977987).

The spelling of 66761221 in words is "sixty-six million, seven hundred sixty-one thousand, two hundred twenty-one".