66361781 has 2 divisors, whose sum is σ = 66361782. Its totient is φ = 66361780.

The previous prime is 66361759. The next prime is 66361787. The reversal of 66361781 is 18716366.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 46922500 + 19439281 = 6850^2 + 4409^2 .

It is a cyclic number.

It is not a de Polignac number, because 66361781 - 2²² = 62167477 is a prime.

It is a super-2 number, since 2×66361781² = 8807771954983922, 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 (66361787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33180890 + 33180891.

It is an arithmetic number, because the mean of its divisors is an integer number (33180891).

Almost surely, 2^66361781 is an apocalyptic number.

It is an amenable number.

66361781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66361781 is an equidigital number, since it uses as much as digits as its factorization.

66361781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 38.

The square root of 66361781 is about 8146.2740562787. The cubic root of 66361781 is about 404.8610629455.

The spelling of 66361781 in words is "sixty-six million, three hundred sixty-one thousand, seven hundred eighty-one".