81991270217 has 8 divisors (see below), whose sum is σ = 83762608896. Its totient is φ = 80221050112.

The previous prime is 81991270211. The next prime is 81991270223. The reversal of 81991270217 is 71207219918.

It is an interprime number because it is at equal distance from previous prime (81991270211) and next prime (81991270223).

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 81991270217 - 2¹⁴ = 81991253833 is a prime.

It is a super-2 number, since 2×81991270217² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is not an unprimeable number, because it can be changed into a prime (81991270211) 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, 130613 + ... + 425490.

It is an arithmetic number, because the mean of its divisors is an integer number (10470326112).

Almost surely, 2^81991270217 is an apocalyptic number.

It is an amenable number.

81991270217 is a deficient number, since it is larger than the sum of its proper divisors (1771338679).

81991270217 is a wasteful number, since it uses less digits than its factorization.

81991270217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 559287.

The product of its (nonzero) digits is 127008, while the sum is 47.

The spelling of 81991270217 in words is "eighty-one billion, nine hundred ninety-one million, two hundred seventy thousand, two hundred seventeen".