666506261 has 2 divisors, whose sum is σ = 666506262. Its totient is φ = 666506260.

The previous prime is 666506237. The next prime is 666506273. The reversal of 666506261 is 162605666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 664041361 + 2464900 = 25769^2 + 1570^2 .

It is a cyclic number.

It is not a de Polignac number, because 666506261 - 2²² = 662311957 is a prime.

It is a Chen prime.

It is equal to p_34606496 and since 666506261 and 34606496 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666506461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333253130 + 333253131.

It is an arithmetic number, because the mean of its divisors is an integer number (333253131).

Almost surely, 2^666506261 is an apocalyptic number.

It is an amenable number.

666506261 is a deficient number, since it is larger than the sum of its proper divisors (1).

666506261 is an equidigital number, since it uses as much as digits as its factorization.

666506261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 77760, while the sum is 38.

The square root of 666506261 is about 25816.7825454684. The cubic root of 666506261 is about 873.5103954878.

The spelling of 666506261 in words is "six hundred sixty-six million, five hundred six thousand, two hundred sixty-one".