81787925 has 6 divisors (see below), whose sum is σ = 101417058. Its totient is φ = 65430320.

The previous prime is 81787921. The next prime is 81787939. The reversal of 81787925 is 52978718.

It can be written as a sum of positive squares in 3 ways, for example, as 481636 + 81306289 = 694^2 + 9017^2 .

It is not a de Polignac number, because 81787925 - 2² = 81787921 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81787925.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81787921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1635734 + ... + 1635783.

It is an arithmetic number, because the mean of its divisors is an integer number (16902843).

Almost surely, 2^81787925 is an apocalyptic number.

It is an amenable number.

81787925 is a deficient number, since it is larger than the sum of its proper divisors (19629133).

81787925 is a wasteful number, since it uses less digits than its factorization.

81787925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3271527 (or 3271522 counting only the distinct ones).

The product of its digits is 282240, while the sum is 47.

The square root of 81787925 is about 9043.6676741243. The cubic root of 81787925 is about 434.0732903048.

The spelling of 81787925 in words is "eighty-one million, seven hundred eighty-seven thousand, nine hundred twenty-five".