66888781 has 2 divisors, whose sum is σ = 66888782. Its totient is φ = 66888780.

The previous prime is 66888709. The next prime is 66888791. The reversal of 66888781 is 18788866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37088100 + 29800681 = 6090^2 + 5459^2 .

It is a cyclic number.

It is not a de Polignac number, because 66888781 - 2²³ = 58500173 is a prime.

It is a super-2 number, since 2×66888781² = 8948218047331922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66888791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33444390 + 33444391.

It is an arithmetic number, because the mean of its divisors is an integer number (33444391).

Almost surely, 2^66888781 is an apocalyptic number.

It is an amenable number.

66888781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66888781 is an equidigital number, since it uses as much as digits as its factorization.

66888781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1032192, while the sum is 52.

The square root of 66888781 is about 8178.5561684199. The cubic root of 66888781 is about 405.9299486022.

The spelling of 66888781 in words is "sixty-six million, eight hundred eighty-eight thousand, seven hundred eighty-one".