81231213218 has 4 divisors (see below), whose sum is σ = 121846819830. Its totient is φ = 40615606608.

The previous prime is 81231213199. The next prime is 81231213293.

81231213218 is nontrivially palindromic in base 10.

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

It can be written as a sum of positive squares in only one way, i.e., 62776805809 + 18454407409 = 250553^2 + 135847^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20307803303 + ... + 20307803306.

Almost surely, 2^81231213218 is an apocalyptic number.

81231213218 is a deficient number, since it is larger than the sum of its proper divisors (40615606612).

81231213218 is a wasteful number, since it uses less digits than its factorization.

81231213218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40615606611.

The product of its digits is 4608, while the sum is 32.

The spelling of 81231213218 in words is "eighty-one billion, two hundred thirty-one million, two hundred thirteen thousand, two hundred eighteen".