66821605 has 8 divisors (see below), whose sum is σ = 81699192. Its totient is φ = 52448448.

The previous prime is 66821591. The next prime is 66821621. The reversal of 66821605 is 50612866.

It can be written as a sum of positive squares in 4 ways, for example, as 31787044 + 35034561 = 5638^2 + 5919^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66821605 - 2⁷ = 66821477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 125814 + ... + 126343.

It is an arithmetic number, because the mean of its divisors is an integer number (10212399).

Almost surely, 2^66821605 is an apocalyptic number.

It is an amenable number.

66821605 is a deficient number, since it is larger than the sum of its proper divisors (14877587).

66821605 is a wasteful number, since it uses less digits than its factorization.

66821605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252215.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 66821605 is about 8174.4482994267. The cubic root of 66821605 is about 405.7940120842.

The spelling of 66821605 in words is "sixty-six million, eight hundred twenty-one thousand, six hundred five".