66887721 has 16 divisors (see below), whose sum is σ = 101203200. Its totient is φ = 43642224.

The previous prime is 66887719. The next prime is 66887729. The reversal of 66887721 is 12778866.

66887721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 66887721 - 2¹ = 66887719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66887729) 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, 25086 + ... + 27623.

It is an arithmetic number, because the mean of its divisors is an integer number (6325200).

Almost surely, 2^66887721 is an apocalyptic number.

It is an amenable number.

66887721 is a deficient number, since it is larger than the sum of its proper divisors (34315479).

66887721 is a wasteful number, since it uses less digits than its factorization.

66887721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52765 (or 52759 counting only the distinct ones).

The product of its digits is 225792, while the sum is 45.

The square root of 66887721 is about 8178.4913645488. The cubic root of 66887721 is about 405.9278043063.

The spelling of 66887721 in words is "sixty-six million, eight hundred eighty-seven thousand, seven hundred twenty-one".