66642409 has 2 divisors, whose sum is σ = 66642410. Its totient is φ = 66642408.

The previous prime is 66642379. The next prime is 66642419. The reversal of 66642409 is 90424666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66504025 + 138384 = 8155^2 + 372^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66642409 is a prime.

It is not a weakly prime, because it can be changed into another prime (66642419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33321204 + 33321205.

It is an arithmetic number, because the mean of its divisors is an integer number (33321205).

Almost surely, 2^66642409 is an apocalyptic number.

It is an amenable number.

66642409 is a deficient number, since it is larger than the sum of its proper divisors (1).

66642409 is an equidigital number, since it uses as much as digits as its factorization.

66642409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62208, while the sum is 37.

The square root of 66642409 is about 8163.4802014827. The cubic root of 66642409 is about 405.4309470625.

The spelling of 66642409 in words is "sixty-six million, six hundred forty-two thousand, four hundred nine".