81218465663 has 4 divisors (see below), whose sum is σ = 84019102440. Its totient is φ = 78417828888.

The previous prime is 81218465611. The next prime is 81218465711. The reversal of 81218465663 is 36656481218.

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

It is a cyclic number.

It is not a de Polignac number, because 81218465663 - 2³⁰ = 80144723839 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 (81218365663) 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, 1400318345 + ... + 1400318402.

It is an arithmetic number, because the mean of its divisors is an integer number (21004775610).

Almost surely, 2^81218465663 is an apocalyptic number.

81218465663 is a deficient number, since it is larger than the sum of its proper divisors (2800636777).

81218465663 is a wasteful number, since it uses less digits than its factorization.

81218465663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2800636776.

The product of its digits is 1658880, while the sum is 50.

The spelling of 81218465663 in words is "eighty-one billion, two hundred eighteen million, four hundred sixty-five thousand, six hundred sixty-three".