81440105 has 4 divisors (see below), whose sum is σ = 97728132. Its totient is φ = 65152080.

The previous prime is 81440101. The next prime is 81440123. The reversal of 81440105 is 50104418.

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 17007376 + 64432729 = 4124^2 + 8027^2 .

It is not a de Polignac number, because 81440105 - 2² = 81440101 is a prime.

It is a super-2 number, since 2×81440105² = 13264981404822050, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81440101) 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, 8144006 + ... + 8144015.

It is an arithmetic number, because the mean of its divisors is an integer number (24432033).

Almost surely, 2^81440105 is an apocalyptic number.

It is an amenable number.

81440105 is a deficient number, since it is larger than the sum of its proper divisors (16288027).

81440105 is a wasteful number, since it uses less digits than its factorization.

81440105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16288026.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 81440105 is about 9024.4171556949. The cubic root of 81440105 is about 433.4570872709.

The spelling of 81440105 in words is "eighty-one million, four hundred forty thousand, one hundred five".