81310120217 has 2 divisors, whose sum is σ = 81310120218. Its totient is φ = 81310120216.

The previous prime is 81310120201. The next prime is 81310120277. The reversal of 81310120217 is 71202101318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75572209216 + 5737911001 = 274904^2 + 75749^2 .

It is a cyclic number.

It is not a de Polignac number, because 81310120217 - 2⁴ = 81310120201 is a prime.

It is a super-3 number, since 3×81310120217³ (a number of 34 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (81310120277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40655060108 + 40655060109.

It is an arithmetic number, because the mean of its divisors is an integer number (40655060109).

Almost surely, 2^81310120217 is an apocalyptic number.

It is an amenable number.

81310120217 is a deficient number, since it is larger than the sum of its proper divisors (1).

81310120217 is an equidigital number, since it uses as much as digits as its factorization.

81310120217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 26.

The spelling of 81310120217 in words is "eighty-one billion, three hundred ten million, one hundred twenty thousand, two hundred seventeen".