66649421 has 2 divisors, whose sum is σ = 66649422. Its totient is φ = 66649420.

The previous prime is 66649403. The next prime is 66649433. The reversal of 66649421 is 12494666.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43705321 + 22944100 = 6611^2 + 4790^2 .

It is a cyclic number.

It is not a de Polignac number, because 66649421 - 2⁶ = 66649357 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66649481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33324710 + 33324711.

It is an arithmetic number, because the mean of its divisors is an integer number (33324711).

Almost surely, 2^66649421 is an apocalyptic number.

It is an amenable number.

66649421 is a deficient number, since it is larger than the sum of its proper divisors (1).

66649421 is an equidigital number, since it uses as much as digits as its factorization.

66649421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 38.

The square root of 66649421 is about 8163.9096638804. The cubic root of 66649421 is about 405.4451661468.

The spelling of 66649421 in words is "sixty-six million, six hundred forty-nine thousand, four hundred twenty-one".