66742810821 has 24 divisors (see below), whose sum is σ = 96875527320. Its totient is φ = 44278972416.

The previous prime is 66742810817. The next prime is 66742810877. The reversal of 66742810821 is 12801824766.

It can be written as a sum of positive squares in 4 ways, for example, as 11190677796 + 55552133025 = 105786^2 + 235695^2 .

It is not a de Polignac number, because 66742810821 - 2² = 66742810817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66742410821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2459101 + ... + 2486093.

It is an arithmetic number, because the mean of its divisors is an integer number (4036480305).

Almost surely, 2^66742810821 is an apocalyptic number.

It is an amenable number.

66742810821 is a deficient number, since it is larger than the sum of its proper divisors (30132716499).

66742810821 is a wasteful number, since it uses less digits than its factorization.

66742810821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28325 (or 28322 counting only the distinct ones).

The product of its (nonzero) digits is 258048, while the sum is 45.

The spelling of 66742810821 in words is "sixty-six billion, seven hundred forty-two million, eight hundred ten thousand, eight hundred twenty-one".