66642021 has 24 divisors (see below), whose sum is σ = 100595040. Its totient is φ = 44086032.

The previous prime is 66642011. The next prime is 66642047. The reversal of 66642021 is 12024666.

It is a happy number.

It is not a de Polignac number, because 66642021 - 2⁷ = 66641893 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66642011) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 32791 + ... + 34763.

It is an arithmetic number, because the mean of its divisors is an integer number (4191460).

Almost surely, 2^66642021 is an apocalyptic number.

It is an amenable number.

66642021 is a deficient number, since it is larger than the sum of its proper divisors (33953019).

66642021 is a wasteful number, since it uses less digits than its factorization.

66642021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2127 (or 2115 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 66642021 is about 8163.4564370737. The cubic root of 66642021 is about 405.4301602387.

Adding to 66642021 its reverse (12024666), we get a palindrome (78666687).

The spelling of 66642021 in words is "sixty-six million, six hundred forty-two thousand, twenty-one".