66906421 has 2 divisors, whose sum is σ = 66906422. Its totient is φ = 66906420.

The previous prime is 66906361. The next prime is 66906457. The reversal of 66906421 is 12460966.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47458321 + 19448100 = 6889^2 + 4410^2 .

It is a cyclic number.

It is not a de Polignac number, because 66906421 - 2¹³ = 66898229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66906461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33453210 + 33453211.

It is an arithmetic number, because the mean of its divisors is an integer number (33453211).

Almost surely, 2^66906421 is an apocalyptic number.

It is an amenable number.

66906421 is a deficient number, since it is larger than the sum of its proper divisors (1).

66906421 is an equidigital number, since it uses as much as digits as its factorization.

66906421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15552, while the sum is 34.

The square root of 66906421 is about 8179.6345272879. The cubic root of 66906421 is about 405.9656295979.

The spelling of 66906421 in words is "sixty-six million, nine hundred six thousand, four hundred twenty-one".