66653681 has 2 divisors, whose sum is σ = 66653682. Its totient is φ = 66653680.

The previous prime is 66653641. The next prime is 66653683. The reversal of 66653681 is 18635666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60202081 + 6451600 = 7759^2 + 2540^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66653681 is a prime.

It is a super-2 number, since 2×66653681² = 8885426381699522, which contains 22 as substring.

Together with 66653683, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (66653683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33326840 + 33326841.

It is an arithmetic number, because the mean of its divisors is an integer number (33326841).

Almost surely, 2^66653681 is an apocalyptic number.

It is an amenable number.

66653681 is a deficient number, since it is larger than the sum of its proper divisors (1).

66653681 is an equidigital number, since it uses as much as digits as its factorization.

66653681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 155520, while the sum is 41.

The square root of 66653681 is about 8164.1705641173. The cubic root of 66653681 is about 405.4538041794.

The spelling of 66653681 in words is "sixty-six million, six hundred fifty-three thousand, six hundred eighty-one".