81857357 has 4 divisors (see below), whose sum is σ = 84069756. Its totient is φ = 79644960.

The previous prime is 81857353. The next prime is 81857371. The reversal of 81857357 is 75375818.

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 36348841 + 45508516 = 6029^2 + 6746^2 .

It is a cyclic number.

It is not a de Polignac number, because 81857357 - 2² = 81857353 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 (81857353) 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, 1106144 + ... + 1106217.

It is an arithmetic number, because the mean of its divisors is an integer number (21017439).

Almost surely, 2^81857357 is an apocalyptic number.

It is an amenable number.

81857357 is a deficient number, since it is larger than the sum of its proper divisors (2212399).

81857357 is a wasteful number, since it uses less digits than its factorization.

81857357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2212398.

The product of its digits is 235200, while the sum is 44.

The square root of 81857357 is about 9047.5055678347. The cubic root of 81857357 is about 434.1960877806.

The spelling of 81857357 in words is "eighty-one million, eight hundred fifty-seven thousand, three hundred fifty-seven".