66731557 has 2 divisors, whose sum is σ = 66731558. Its totient is φ = 66731556.

The previous prime is 66731549. The next prime is 66731573. The reversal of 66731557 is 75513766.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43441281 + 23290276 = 6591^2 + 4826^2 .

It is a cyclic number.

It is not a de Polignac number, because 66731557 - 2³ = 66731549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66731507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33365778 + 33365779.

It is an arithmetic number, because the mean of its divisors is an integer number (33365779).

Almost surely, 2^66731557 is an apocalyptic number.

It is an amenable number.

66731557 is a deficient number, since it is larger than the sum of its proper divisors (1).

66731557 is an equidigital number, since it uses as much as digits as its factorization.

66731557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 132300, while the sum is 40.

The square root of 66731557 is about 8168.9385479388. The cubic root of 66731557 is about 405.6116490818.

The spelling of 66731557 in words is "sixty-six million, seven hundred thirty-one thousand, five hundred fifty-seven".