66045781 has 2 divisors, whose sum is σ = 66045782. Its totient is φ = 66045780.

The previous prime is 66045761. The next prime is 66045787. The reversal of 66045781 is 18754066.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64545156 + 1500625 = 8034^2 + 1225^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66045781 is a prime.

It is a super-2 number, since 2×66045781² = 8724090375799922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 66045781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66045787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33022890 + 33022891.

It is an arithmetic number, because the mean of its divisors is an integer number (33022891).

Almost surely, 2^66045781 is an apocalyptic number.

It is an amenable number.

66045781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66045781 is an equidigital number, since it uses as much as digits as its factorization.

66045781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40320, while the sum is 37.

The square root of 66045781 is about 8126.8555419670. The cubic root of 66045781 is about 404.2174208743.

The spelling of 66045781 in words is "sixty-six million, forty-five thousand, seven hundred eighty-one".