66644921 has 4 divisors (see below), whose sum is σ = 76165632. Its totient is φ = 57124212.

The previous prime is 66644887. The next prime is 66644923. The reversal of 66644921 is 12944666.

It is a happy number.

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 66644921 - 2¹⁸ = 66382777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66644923) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4760345 + ... + 4760358.

It is an arithmetic number, because the mean of its divisors is an integer number (19041408).

Almost surely, 2^66644921 is an apocalyptic number.

It is an amenable number.

66644921 is a deficient number, since it is larger than the sum of its proper divisors (9520711).

66644921 is an equidigital number, since it uses as much as digits as its factorization.

66644921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9520710.

The product of its digits is 62208, while the sum is 38.

The square root of 66644921 is about 8163.6340559827. The cubic root of 66644921 is about 405.4360410648.

The spelling of 66644921 in words is "sixty-six million, six hundred forty-four thousand, nine hundred twenty-one".