81320511 has 4 divisors (see below), whose sum is σ = 108427352. Its totient is φ = 54213672.

The previous prime is 81320501. The next prime is 81320527. The reversal of 81320511 is 11502318.

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

It is not a de Polignac number, because 81320511 - 2¹⁷ = 81189439 is a prime.

It is a super-2 number, since 2×81320511² = 13226051018602242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81320501) 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, 13553416 + ... + 13553421.

It is an arithmetic number, because the mean of its divisors is an integer number (27106838).

Almost surely, 2^81320511 is an apocalyptic number.

81320511 is a deficient number, since it is larger than the sum of its proper divisors (27106841).

81320511 is a wasteful number, since it uses less digits than its factorization.

81320511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27106840.

The product of its (nonzero) digits is 240, while the sum is 21.

The square root of 81320511 is about 9017.7885870096. The cubic root of 81320511 is about 433.2448074915.

Adding to 81320511 its reverse (11502318), we get a palindrome (92822829).

The spelling of 81320511 in words is "eighty-one million, three hundred twenty thousand, five hundred eleven".