81851071 has 4 divisors (see below), whose sum is σ = 82190944. Its totient is φ = 81511200.

The previous prime is 81850999. The next prime is 81851083. The reversal of 81851071 is 17015818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17015818 = 2 ⋅8507909.

It is a cyclic number.

It is not a de Polignac number, because 81851071 - 2¹¹ = 81849023 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 (81851171) 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, 169575 + ... + 170056.

It is an arithmetic number, because the mean of its divisors is an integer number (20547736).

Almost surely, 2^81851071 is an apocalyptic number.

81851071 is a deficient number, since it is larger than the sum of its proper divisors (339873).

81851071 is a wasteful number, since it uses less digits than its factorization.

81851071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339872.

The product of its (nonzero) digits is 2240, while the sum is 31.

The square root of 81851071 is about 9047.1581725976. The cubic root of 81851071 is about 434.1849732167.

Adding to 81851071 its reverse (17015818), we get a palindrome (98866889).

The spelling of 81851071 in words is "eighty-one million, eight hundred fifty-one thousand, seventy-one".