81577218813 has 4 divisors (see below), whose sum is σ = 108769625088. Its totient is φ = 54384812540.

The previous prime is 81577218803. The next prime is 81577218839. The reversal of 81577218813 is 31881277518.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81577218813 - 2⁸ = 81577218557 is a prime.

It is a super-2 number, since 2×81577218813² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81577218803) 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, 13596203133 + ... + 13596203138.

It is an arithmetic number, because the mean of its divisors is an integer number (27192406272).

Almost surely, 2^81577218813 is an apocalyptic number.

It is an amenable number.

81577218813 is a deficient number, since it is larger than the sum of its proper divisors (27192406275).

81577218813 is a wasteful number, since it uses less digits than its factorization.

81577218813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27192406274.

The product of its digits is 752640, while the sum is 51.

The spelling of 81577218813 in words is "eighty-one billion, five hundred seventy-seven million, two hundred eighteen thousand, eight hundred thirteen".