66228921 has 32 divisors (see below), whose sum is σ = 108397440. Its totient is φ = 40124160.

The previous prime is 66228919. The next prime is 66228941. The reversal of 66228921 is 12982266.

It is a happy number.

66228921 is a `hidden beast` number, since 6 + 622 + 8 + 9 + 21 = 666.

It is not a de Polignac number, because 66228921 - 2¹ = 66228919 is a prime.

It is a super-3 number, since 3×66228921³ (a number of 24 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (66228941) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22681 + ... + 25433.

It is an arithmetic number, because the mean of its divisors is an integer number (3387420).

Almost surely, 2^66228921 is an apocalyptic number.

It is an amenable number.

66228921 is a deficient number, since it is larger than the sum of its proper divisors (42168519).

66228921 is an equidigital number, since it uses as much as digits as its factorization.

66228921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2785 (or 2767 counting only the distinct ones).

The product of its digits is 20736, while the sum is 36.

The square root of 66228921 is about 8138.1153223581. The cubic root of 66228921 is about 404.5906976000.

The spelling of 66228921 in words is "sixty-six million, two hundred twenty-eight thousand, nine hundred twenty-one".