66550721 has 2 divisors, whose sum is σ = 66550722. Its totient is φ = 66550720.

The previous prime is 66550717. The next prime is 66550741. The reversal of 66550721 is 12705566.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 62094400 + 4456321 = 7880^2 + 2111^2 .

It is a cyclic number.

It is not a de Polignac number, because 66550721 - 2² = 66550717 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (66550741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33275360 + 33275361.

It is an arithmetic number, because the mean of its divisors is an integer number (33275361).

Almost surely, 2^66550721 is an apocalyptic number.

It is an amenable number.

66550721 is a deficient number, since it is larger than the sum of its proper divisors (1).

66550721 is an equidigital number, since it uses as much as digits as its factorization.

66550721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12600, while the sum is 32.

The square root of 66550721 is about 8157.8625264220. The cubic root of 66550721 is about 405.2449283089.

The spelling of 66550721 in words is "sixty-six million, five hundred fifty thousand, seven hundred twenty-one".