66242809 has 2 divisors, whose sum is σ = 66242810. Its totient is φ = 66242808.

The previous prime is 66242807. The next prime is 66242831. The reversal of 66242809 is 90824266.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41641209 + 24601600 = 6453^2 + 4960^2 .

It is a cyclic number.

It is not a de Polignac number, because 66242809 - 2¹ = 66242807 is a prime.

Together with 66242807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (66242801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33121404 + 33121405.

It is an arithmetic number, because the mean of its divisors is an integer number (33121405).

Almost surely, 2^66242809 is an apocalyptic number.

It is an amenable number.

66242809 is a deficient number, since it is larger than the sum of its proper divisors (1).

66242809 is an equidigital number, since it uses as much as digits as its factorization.

66242809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 41472, while the sum is 37.

The square root of 66242809 is about 8138.9685464437. The cubic root of 66242809 is about 404.6189760963.

The spelling of 66242809 in words is "sixty-six million, two hundred forty-two thousand, eight hundred nine".