65688721 has 16 divisors (see below), whose sum is σ = 77856768. Its totient is φ = 54234000.

The previous prime is 65688709. The next prime is 65688739. The reversal of 65688721 is 12788656.

65688721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 65688721 - 2⁷ = 65688593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (65688781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56496 + ... + 57646.

It is an arithmetic number, because the mean of its divisors is an integer number (4866048).

Almost surely, 2^65688721 is an apocalyptic number.

It is an amenable number.

65688721 is a deficient number, since it is larger than the sum of its proper divisors (12168047).

65688721 is a wasteful number, since it uses less digits than its factorization.

65688721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1452.

The product of its digits is 161280, while the sum is 43.

The square root of 65688721 is about 8104.8578642688. The cubic root of 65688721 is about 403.4876707496.

The spelling of 65688721 in words is "sixty-five million, six hundred eighty-eight thousand, seven hundred twenty-one".