66143721 has 16 divisors (see below), whose sum is σ = 100951424. Its totient is φ = 37736064.

The previous prime is 66143713. The next prime is 66143723. The reversal of 66143721 is 12734166.

It is not a de Polignac number, because 66143721 - 2³ = 66143713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66143723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13245 + ... + 17541.

It is an arithmetic number, because the mean of its divisors is an integer number (6309464).

Almost surely, 2^66143721 is an apocalyptic number.

It is an amenable number.

66143721 is a deficient number, since it is larger than the sum of its proper divisors (34807703).

66143721 is a wasteful number, since it uses less digits than its factorization.

66143721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5040.

The product of its digits is 6048, while the sum is 30.

The square root of 66143721 is about 8132.8790105350. The cubic root of 66143721 is about 404.4171283131.

Adding to 66143721 its reverse (12734166), we get a palindrome (78877887).

The spelling of 66143721 in words is "sixty-six million, one hundred forty-three thousand, seven hundred twenty-one".