66816823 has 4 divisors (see below), whose sum is σ = 66893040. Its totient is φ = 66740608.

The previous prime is 66816809. The next prime is 66816829. The reversal of 66816823 is 32861866.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 32861866 = 2 ⋅16430933.

It is a cyclic number.

It is not a de Polignac number, because 66816823 - 2⁵ = 66816791 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66816829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36778 + ... + 38551.

It is an arithmetic number, because the mean of its divisors is an integer number (16723260).

Almost surely, 2^66816823 is an apocalyptic number.

66816823 is a deficient number, since it is larger than the sum of its proper divisors (76217).

66816823 is an equidigital number, since it uses as much as digits as its factorization.

66816823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76216.

The product of its digits is 82944, while the sum is 40.

The square root of 66816823 is about 8174.1557973897. The cubic root of 66816823 is about 405.7843318156.

The spelling of 66816823 in words is "sixty-six million, eight hundred sixteen thousand, eight hundred twenty-three".