66173909 has 2 divisors, whose sum is σ = 66173910. Its totient is φ = 66173908.

The previous prime is 66173897. The next prime is 66173923. The reversal of 66173909 is 90937166.

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., 65966884 + 207025 = 8122^2 + 455^2 .

It is a cyclic number.

It is not a de Polignac number, because 66173909 - 2¹² = 66169813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66173929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33086954 + 33086955.

It is an arithmetic number, because the mean of its divisors is an integer number (33086955).

Almost surely, 2^66173909 is an apocalyptic number.

It is an amenable number.

66173909 is a deficient number, since it is larger than the sum of its proper divisors (1).

66173909 is an equidigital number, since it uses as much as digits as its factorization.

66173909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 61236, while the sum is 41.

The square root of 66173909 is about 8134.7347221652. The cubic root of 66173909 is about 404.4786442929.

The spelling of 66173909 in words is "sixty-six million, one hundred seventy-three thousand, nine hundred nine".