66646421 has 2 divisors, whose sum is σ = 66646422. Its totient is φ = 66646420.

The previous prime is 66646403. The next prime is 66646429. The reversal of 66646421 is 12464666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50566321 + 16080100 = 7111^2 + 4010^2 .

It is a cyclic number.

It is not a de Polignac number, because 66646421 - 2¹⁴ = 66630037 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66646429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33323210 + 33323211.

It is an arithmetic number, because the mean of its divisors is an integer number (33323211).

Almost surely, 2^66646421 is an apocalyptic number.

It is an amenable number.

66646421 is a deficient number, since it is larger than the sum of its proper divisors (1).

66646421 is an equidigital number, since it uses as much as digits as its factorization.

66646421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 35.

The square root of 66646421 is about 8163.7259263158. The cubic root of 66646421 is about 405.4390828044.

The spelling of 66646421 in words is "sixty-six million, six hundred forty-six thousand, four hundred twenty-one".