81391229 has 4 divisors (see below), whose sum is σ = 81633084. Its totient is φ = 81149376.

The previous prime is 81391207. The next prime is 81391237. The reversal of 81391229 is 92219318.

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 6100900 + 75290329 = 2470^2 + 8677^2 .

It is a cyclic number.

It is not a de Polignac number, because 81391229 - 2⁸ = 81390973 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 (81391249) 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, 120422 + ... + 121095.

It is an arithmetic number, because the mean of its divisors is an integer number (20408271).

Almost surely, 2^81391229 is an apocalyptic number.

It is an amenable number.

81391229 is a deficient number, since it is larger than the sum of its proper divisors (241855).

81391229 is a wasteful number, since it uses less digits than its factorization.

81391229 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241854.

The product of its digits is 7776, while the sum is 35.

The square root of 81391229 is about 9021.7087627566. The cubic root of 81391229 is about 433.3703573231.

The spelling of 81391229 in words is "eighty-one million, three hundred ninety-one thousand, two hundred twenty-nine".