66781679 has 2 divisors, whose sum is σ = 66781680. Its totient is φ = 66781678.

The previous prime is 66781601. The next prime is 66781681. The reversal of 66781679 is 97618766.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66781679 - 2¹² = 66777583 is a prime.

It is a Sophie Germain prime.

Together with 66781681, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66781699) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33390839 + 33390840.

It is an arithmetic number, because the mean of its divisors is an integer number (33390840).

Almost surely, 2^66781679 is an apocalyptic number.

66781679 is a deficient number, since it is larger than the sum of its proper divisors (1).

66781679 is an equidigital number, since it uses as much as digits as its factorization.

66781679 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 762048, while the sum is 50.

The square root of 66781679 is about 8172.0058125285. The cubic root of 66781679 is about 405.7131751571.

The spelling of 66781679 in words is "sixty-six million, seven hundred eighty-one thousand, six hundred seventy-nine".