66240021 has 12 divisors (see below), whose sum is σ = 89370528. Its totient is φ = 43636824.

The previous prime is 66240017. The next prime is 66240037. The reversal of 66240021 is 12004266.

It is a happy number.

It is not a de Polignac number, because 66240021 - 2² = 66240017 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66240021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66240001) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 142836 + ... + 143298.

It is an arithmetic number, because the mean of its divisors is an integer number (7447544).

Almost surely, 2^66240021 is an apocalyptic number.

It is an amenable number.

66240021 is a deficient number, since it is larger than the sum of its proper divisors (23130507).

66240021 is an equidigital number, since it uses as much as digits as its factorization.

66240021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1032 (or 569 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 66240021 is about 8138.7972698673. The cubic root of 66240021 is about 404.6132995378.

Adding to 66240021 its reverse (12004266), we get a palindrome (78244287).

The spelling of 66240021 in words is "sixty-six million, two hundred forty thousand, twenty-one".