81951568217 has 8 divisors (see below), whose sum is σ = 85013053440. Its totient is φ = 78940686240.

The previous prime is 81951568207. The next prime is 81951568219. The reversal of 81951568217 is 71286515918.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81951568217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81951568219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12647513 + ... + 12653990.

It is an arithmetic number, because the mean of its divisors is an integer number (10626631680).

Almost surely, 2^81951568217 is an apocalyptic number.

It is an amenable number.

81951568217 is a deficient number, since it is larger than the sum of its proper divisors (3061485223).

81951568217 is a wasteful number, since it uses less digits than its factorization.

81951568217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25301623.

The product of its digits is 1209600, while the sum is 53.

The spelling of 81951568217 in words is "eighty-one billion, nine hundred fifty-one million, five hundred sixty-eight thousand, two hundred seventeen".