81944413 has 4 divisors (see below), whose sum is σ = 83490588. Its totient is φ = 80398240.

The previous prime is 81944407. The next prime is 81944441. The reversal of 81944413 is 31444918.

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 30492484 + 51451929 = 5522^2 + 7173^2 .

It is a cyclic number.

It is not a de Polignac number, because 81944413 - 2¹⁷ = 81813341 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81944483) 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, 773008 + ... + 773113.

It is an arithmetic number, because the mean of its divisors is an integer number (20872647).

Almost surely, 2^81944413 is an apocalyptic number.

It is an amenable number.

81944413 is a deficient number, since it is larger than the sum of its proper divisors (1546175).

81944413 is a wasteful number, since it uses less digits than its factorization.

81944413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1546174.

The product of its digits is 13824, while the sum is 34.

The square root of 81944413 is about 9052.3153391826. The cubic root of 81944413 is about 434.3499569987.

The spelling of 81944413 in words is "eighty-one million, nine hundred forty-four thousand, four hundred thirteen".