81238927249 has 4 divisors (see below), whose sum is σ = 81242408164. Its totient is φ = 81235446336.

The previous prime is 81238927219. The next prime is 81238927283. The reversal of 81238927249 is 94272983218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 94272983218 = 2 ⋅47136491609.

It can be written as a sum of positive squares in 2 ways, for example, as 66457230849 + 14781696400 = 257793^2 + 121580^2 .

It is a cyclic number.

It is not a de Polignac number, because 81238927249 - 2⁹ = 81238926737 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81238927249.

It is not an unprimeable number, because it can be changed into a prime (81238927219) 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, 1705212 + ... + 1752205.

It is an arithmetic number, because the mean of its divisors is an integer number (20310602041).

Almost surely, 2^81238927249 is an apocalyptic number.

It is an amenable number.

81238927249 is a deficient number, since it is larger than the sum of its proper divisors (3480915).

81238927249 is a wasteful number, since it uses less digits than its factorization.

81238927249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3480914.

The product of its digits is 3483648, while the sum is 55.

The spelling of 81238927249 in words is "eighty-one billion, two hundred thirty-eight million, nine hundred twenty-seven thousand, two hundred forty-nine".