66697661 has 2 divisors, whose sum is σ = 66697662. Its totient is φ = 66697660.

The previous prime is 66697649. The next prime is 66697663. The reversal of 66697661 is 16679666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37332100 + 29365561 = 6110^2 + 5419^2 .

It is a cyclic number.

It is not a de Polignac number, because 66697661 - 2⁶ = 66697597 is a prime.

Together with 66697663, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66697663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33348830 + 33348831.

It is an arithmetic number, because the mean of its divisors is an integer number (33348831).

Almost surely, 2^66697661 is an apocalyptic number.

It is an amenable number.

66697661 is a deficient number, since it is larger than the sum of its proper divisors (1).

66697661 is an equidigital number, since it uses as much as digits as its factorization.

66697661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 489888, while the sum is 47.

The square root of 66697661 is about 8166.8635962651. The cubic root of 66697661 is about 405.5429612347.

The spelling of 66697661 in words is "sixty-six million, six hundred ninety-seven thousand, six hundred sixty-one".