66404821 has 16 divisors (see below), whose sum is σ = 79126528. Its totient is φ = 54529200.

The previous prime is 66404803. The next prime is 66404827. The reversal of 66404821 is 12840466.

It is a cyclic number.

It is not a de Polignac number, because 66404821 - 2¹¹ = 66402773 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66404827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20866 + ... + 23836.

It is an arithmetic number, because the mean of its divisors is an integer number (4945408).

Almost surely, 2^66404821 is an apocalyptic number.

It is an amenable number.

66404821 is a deficient number, since it is larger than the sum of its proper divisors (12721707).

66404821 is a wasteful number, since it uses less digits than its factorization.

66404821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3112.

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 66404821 is about 8148.9153265941. The cubic root of 66404821 is about 404.9485704140.

The spelling of 66404821 in words is "sixty-six million, four hundred four thousand, eight hundred twenty-one".