81286351981 has 4 divisors (see below), whose sum is σ = 81338493600. Its totient is φ = 81234210364.

The previous prime is 81286351957. The next prime is 81286352003. The reversal of 81286351981 is 18915368218.

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 81286351981 - 2⁹ = 81286351469 is a prime.

It is a super-2 number, since 2×81286351981² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81286355981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26068471 + ... + 26071588.

It is an arithmetic number, because the mean of its divisors is an integer number (20334623400).

Almost surely, 2^81286351981 is an apocalyptic number.

It is an amenable number.

81286351981 is a deficient number, since it is larger than the sum of its proper divisors (52141619).

81286351981 is a wasteful number, since it uses less digits than its factorization.

81286351981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52141618.

The product of its digits is 829440, while the sum is 52.

The spelling of 81286351981 in words is "eighty-one billion, two hundred eighty-six million, three hundred fifty-one thousand, nine hundred eighty-one".