65664721 has 8 divisors (see below), whose sum is σ = 67754880. Its totient is φ = 63606192.

The previous prime is 65664691. The next prime is 65664733. The reversal of 65664721 is 12746656.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 65664721 - 2⁵ = 65664689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (65664791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3655 + ... + 12028.

It is an arithmetic number, because the mean of its divisors is an integer number (8469360).

Almost surely, 2^65664721 is an apocalyptic number.

It is an amenable number.

65664721 is a deficient number, since it is larger than the sum of its proper divisors (2090159).

65664721 is a wasteful number, since it uses less digits than its factorization.

65664721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15815.

The product of its digits is 60480, while the sum is 37.

The square root of 65664721 is about 8103.3771354911. The cubic root of 65664721 is about 403.4385254091.

The spelling of 65664721 in words is "sixty-five million, six hundred sixty-four thousand, seven hundred twenty-one".