66408021 has 12 divisors (see below), whose sum is σ = 100971520. Its totient is φ = 41941800.

The previous prime is 66407989. The next prime is 66408031. The reversal of 66408021 is 12080466.

It is not a de Polignac number, because 66408021 - 2⁵ = 66407989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66408031) 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, 194005 + ... + 194346.

Almost surely, 2^66408021 is an apocalyptic number.

It is an amenable number.

66408021 is a deficient number, since it is larger than the sum of its proper divisors (34563499).

66408021 is a wasteful number, since it uses less digits than its factorization.

66408021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388376 (or 388373 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 66408021 is about 8149.1116693784. Note that the first 3 decimals coincide. The cubic root of 66408021 is about 404.9550750351.

Adding to 66408021 its reverse (12080466), we get a palindrome (78488487).

The spelling of 66408021 in words is "sixty-six million, four hundred eight thousand, twenty-one".