66640641 has 4 divisors (see below), whose sum is σ = 88854192. Its totient is φ = 44427092.

The previous prime is 66640601. The next prime is 66640661. The reversal of 66640641 is 14604666.

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 66640641 - 2⁶ = 66640577 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66640601) 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, 11106771 + ... + 11106776.

It is an arithmetic number, because the mean of its divisors is an integer number (22213548).

Almost surely, 2^66640641 is an apocalyptic number.

It is an amenable number.

66640641 is a deficient number, since it is larger than the sum of its proper divisors (22213551).

66640641 is a wasteful number, since it uses less digits than its factorization.

66640641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22213550.

The product of its (nonzero) digits is 20736, while the sum is 33.

The square root of 66640641 is about 8163.3719136151. The cubic root of 66640641 is about 405.4273617167.

The spelling of 66640641 in words is "sixty-six million, six hundred forty thousand, six hundred forty-one".