66429721 has 2 divisors, whose sum is σ = 66429722. Its totient is φ = 66429720.

The previous prime is 66429697. The next prime is 66429731. The reversal of 66429721 is 12792466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66194496 + 235225 = 8136^2 + 485^2 .

It is a cyclic number.

It is not a de Polignac number, because 66429721 - 2⁷ = 66429593 is a prime.

It is not a weakly prime, because it can be changed into another prime (66429731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33214860 + 33214861.

It is an arithmetic number, because the mean of its divisors is an integer number (33214861).

Almost surely, 2^66429721 is an apocalyptic number.

It is an amenable number.

66429721 is a deficient number, since it is larger than the sum of its proper divisors (1).

66429721 is an equidigital number, since it uses as much as digits as its factorization.

66429721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 37.

The square root of 66429721 is about 8150.4429940955. The cubic root of 66429721 is about 404.9991789853. Note that the first 3 decimals are identical.

The spelling of 66429721 in words is "sixty-six million, four hundred twenty-nine thousand, seven hundred twenty-one".