66806921869 has 4 divisors (see below), whose sum is σ = 69110608860. Its totient is φ = 64503234880.

The previous prime is 66806921837. The next prime is 66806921873. The reversal of 66806921869 is 96812960866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17046696969 + 49760224900 = 130563^2 + 223070^2 .

It is a cyclic number.

It is not a de Polignac number, because 66806921869 - 2⁵ = 66806921837 is a prime.

It is a super-2 number, since 2×66806921869² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66806921899) 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 in 3 ways as a sum of consecutive naturals, for example, 1151843452 + ... + 1151843509.

It is an arithmetic number, because the mean of its divisors is an integer number (17277652215).

Almost surely, 2^66806921869 is an apocalyptic number.

It is an amenable number.

66806921869 is a deficient number, since it is larger than the sum of its proper divisors (2303686991).

66806921869 is a wasteful number, since it uses less digits than its factorization.

66806921869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2303686990.

The product of its (nonzero) digits is 13436928, while the sum is 61.

The spelling of 66806921869 in words is "sixty-six billion, eight hundred six million, nine hundred twenty-one thousand, eight hundred sixty-nine".