81387822221 has 4 divisors (see below), whose sum is σ = 81621025500. Its totient is φ = 81154618944.

The previous prime is 81387822119. The next prime is 81387822253. The reversal of 81387822221 is 12222878318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 49920964900 + 31466857321 = 223430^2 + 177389^2 .

It is a cyclic number.

It is not a de Polignac number, because 81387822221 - 2¹⁸ = 81387560077 is a prime.

It is a super-3 number, since 3×81387822221³ (a number of 34 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81387822721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 116601116 + ... + 116601813.

It is an arithmetic number, because the mean of its divisors is an integer number (20405256375).

Almost surely, 2^81387822221 is an apocalyptic number.

It is an amenable number.

81387822221 is a deficient number, since it is larger than the sum of its proper divisors (233203279).

81387822221 is a wasteful number, since it uses less digits than its factorization.

81387822221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233203278.

The product of its digits is 172032, while the sum is 44.

The spelling of 81387822221 in words is "eighty-one billion, three hundred eighty-seven million, eight hundred twenty-two thousand, two hundred twenty-one".