66208781 has 2 divisors, whose sum is σ = 66208782. Its totient is φ = 66208780.

The previous prime is 66208771. The next prime is 66208837. The reversal of 66208781 is 18780266.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43494025 + 22714756 = 6595^2 + 4766^2 .

It is a cyclic number.

It is not a de Polignac number, because 66208781 - 2⁶ = 66208717 is a prime.

It is a super-2 number, since 2×66208781² = 8767205363011922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66208771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33104390 + 33104391.

It is an arithmetic number, because the mean of its divisors is an integer number (33104391).

Almost surely, 2^66208781 is an apocalyptic number.

It is an amenable number.

66208781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66208781 is an equidigital number, since it uses as much as digits as its factorization.

66208781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32256, while the sum is 38.

The square root of 66208781 is about 8136.8778410395. The cubic root of 66208781 is about 404.5496818693.

The spelling of 66208781 in words is "sixty-six million, two hundred eight thousand, seven hundred eighty-one".