81981595217 has 8 divisors (see below), whose sum is σ = 83431918080. Its totient is φ = 80533299280.

The previous prime is 81981595183. The next prime is 81981595237. The reversal of 81981595217 is 71259518918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81981595217 - 2¹² = 81981591121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81981595237) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 425009 + ... + 587022.

It is an arithmetic number, because the mean of its divisors is an integer number (10428989760).

Almost surely, 2^81981595217 is an apocalyptic number.

It is an amenable number.

81981595217 is a deficient number, since it is larger than the sum of its proper divisors (1450322863).

81981595217 is a wasteful number, since it uses less digits than its factorization.

81981595217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1013463.

The product of its digits is 1814400, while the sum is 56.

The spelling of 81981595217 in words is "eighty-one billion, nine hundred eighty-one million, five hundred ninety-five thousand, two hundred seventeen".