66545621 has 2 divisors, whose sum is σ = 66545622. Its totient is φ = 66545620.

The previous prime is 66545617. The next prime is 66545629. The reversal of 66545621 is 12654566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43744996 + 22800625 = 6614^2 + 4775^2 .

It is a cyclic number.

It is not a de Polignac number, because 66545621 - 2² = 66545617 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 (66545629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33272810 + 33272811.

It is an arithmetic number, because the mean of its divisors is an integer number (33272811).

Almost surely, 2^66545621 is an apocalyptic number.

It is an amenable number.

66545621 is a deficient number, since it is larger than the sum of its proper divisors (1).

66545621 is an equidigital number, since it uses as much as digits as its factorization.

66545621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43200, while the sum is 35.

The square root of 66545621 is about 8157.5499385539. The cubic root of 66545621 is about 405.2345762952.

The spelling of 66545621 in words is "sixty-six million, five hundred forty-five thousand, six hundred twenty-one".