81157205 has 4 divisors (see below), whose sum is σ = 97388652. Its totient is φ = 64925760.

The previous prime is 81157177. The next prime is 81157207. The reversal of 81157205 is 50275118.

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 18541636 + 62615569 = 4306^2 + 7913^2 .

It is not a de Polignac number, because 81157205 - 2¹² = 81153109 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 (81157207) 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, 8115716 + ... + 8115725.

It is an arithmetic number, because the mean of its divisors is an integer number (24347163).

Almost surely, 2^81157205 is an apocalyptic number.

It is an amenable number.

81157205 is a deficient number, since it is larger than the sum of its proper divisors (16231447).

81157205 is a wasteful number, since it uses less digits than its factorization.

81157205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16231446.

The product of its (nonzero) digits is 2800, while the sum is 29.

The square root of 81157205 is about 9008.7293776648. The cubic root of 81157205 is about 432.9546023552.

The spelling of 81157205 in words is "eighty-one million, one hundred fifty-seven thousand, two hundred five".