81366623 has 4 divisors (see below), whose sum is σ = 87625608. Its totient is φ = 75107640.

The previous prime is 81366613. The next prime is 81366671. The reversal of 81366623 is 32666318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 32666318 = 2 ⋅16333159.

It is a cyclic number.

It is not a de Polignac number, because 81366623 - 2¹⁴ = 81350239 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 (81366613) 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, 3129473 + ... + 3129498.

It is an arithmetic number, because the mean of its divisors is an integer number (21906402).

Almost surely, 2^81366623 is an apocalyptic number.

81366623 is a deficient number, since it is larger than the sum of its proper divisors (6258985).

81366623 is a wasteful number, since it uses less digits than its factorization.

81366623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6258984.

The product of its digits is 31104, while the sum is 35.

The square root of 81366623 is about 9020.3449490582. The cubic root of 81366623 is about 433.3266810945.

It can be divided in two parts, 8 and 1366623, that added together give a palindrome (1366631).

The spelling of 81366623 in words is "eighty-one million, three hundred sixty-six thousand, six hundred twenty-three".