66151721 has 2 divisors, whose sum is σ = 66151722. Its totient is φ = 66151720.

The previous prime is 66151681. The next prime is 66151727. The reversal of 66151721 is 12715166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 48846121 + 17305600 = 6989^2 + 4160^2 .

It is a cyclic number.

It is not a de Polignac number, because 66151721 - 2¹⁰ = 66150697 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (66151727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33075860 + 33075861.

It is an arithmetic number, because the mean of its divisors is an integer number (33075861).

Almost surely, 2^66151721 is an apocalyptic number.

It is an amenable number.

66151721 is a deficient number, since it is larger than the sum of its proper divisors (1).

66151721 is an equidigital number, since it uses as much as digits as its factorization.

66151721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2520, while the sum is 29.

The square root of 66151721 is about 8133.3708264163. The cubic root of 66151721 is about 404.4334322370.

Adding to 66151721 its reverse (12715166), we get a palindrome (78866887).

The spelling of 66151721 in words is "sixty-six million, one hundred fifty-one thousand, seven hundred twenty-one".