81985157 has 4 divisors (see below), whose sum is σ = 82026636. Its totient is φ = 81943680.

The previous prime is 81985151. The next prime is 81985177. The reversal of 81985157 is 75158918.

It is a happy number.

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 45576001 + 36409156 = 6751^2 + 6034^2 .

It is a cyclic number.

It is not a de Polignac number, because 81985157 - 2⁶ = 81985093 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 (81985151) 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, 17618 + ... + 21779.

It is an arithmetic number, because the mean of its divisors is an integer number (20506659).

Almost surely, 2^81985157 is an apocalyptic number.

It is an amenable number.

81985157 is a deficient number, since it is larger than the sum of its proper divisors (41479).

81985157 is a wasteful number, since it uses less digits than its factorization.

81985157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41478.

The product of its digits is 100800, while the sum is 44.

The square root of 81985157 is about 9054.5655334754. The cubic root of 81985157 is about 434.4219335240.

The spelling of 81985157 in words is "eighty-one million, nine hundred eighty-five thousand, one hundred fifty-seven".