66655409 has 2 divisors, whose sum is σ = 66655410. Its totient is φ = 66655408.

The previous prime is 66655387. The next prime is 66655411. The reversal of 66655409 is 90455666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47541025 + 19114384 = 6895^2 + 4372^2 .

It is a cyclic number.

It is not a de Polignac number, because 66655409 - 2²⁴ = 49878193 is a prime.

Together with 66655411, 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 (66655429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33327704 + 33327705.

It is an arithmetic number, because the mean of its divisors is an integer number (33327705).

Almost surely, 2^66655409 is an apocalyptic number.

It is an amenable number.

66655409 is a deficient number, since it is larger than the sum of its proper divisors (1).

66655409 is an equidigital number, since it uses as much as digits as its factorization.

66655409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 194400, while the sum is 41.

The square root of 66655409 is about 8164.2763916957. The cubic root of 66655409 is about 405.4573079525.

The spelling of 66655409 in words is "sixty-six million, six hundred fifty-five thousand, four hundred nine".