66216021 has 4 divisors (see below), whose sum is σ = 88288032. Its totient is φ = 44144012.

The previous prime is 66216013. The next prime is 66216041. The reversal of 66216021 is 12061266.

66216021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66216021 - 2³ = 66216013 is a prime.

It is a super-2 number, since 2×66216021² = 8769122874144882, which contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 66215982 and 66216000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66216041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11036001 + ... + 11036006.

It is an arithmetic number, because the mean of its divisors is an integer number (22072008).

Almost surely, 2^66216021 is an apocalyptic number.

It is an amenable number.

66216021 is a deficient number, since it is larger than the sum of its proper divisors (22072011).

66216021 is a wasteful number, since it uses less digits than its factorization.

66216021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22072010.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 66216021 is about 8137.3227169629. The cubic root of 66216021 is about 404.5644273099.

Adding to 66216021 its reverse (12061266), we get a palindrome (78277287).

The spelling of 66216021 in words is "sixty-six million, two hundred sixteen thousand, twenty-one".