81810125 has 12 divisors (see below), whose sum is σ = 102225396. Its totient is φ = 65367200.

The previous prime is 81810107. The next prime is 81810133. The reversal of 81810125 is 52101818.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 6 ways, for example, as 2439844 + 79370281 = 1562^2 + 8909^2 .

It is not a de Polignac number, because 81810125 - 2⁸ = 81809869 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81810094 and 81810103.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 100721 + ... + 101529.

It is an arithmetic number, because the mean of its divisors is an integer number (8518783).

Almost surely, 2^81810125 is an apocalyptic number.

It is an amenable number.

81810125 is a deficient number, since it is larger than the sum of its proper divisors (20415271).

81810125 is an frugal number, since it uses more digits than its factorization.

81810125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1633 (or 814 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 81810125 is about 9044.8949689866. The cubic root of 81810125 is about 434.1125607933.

The spelling of 81810125 in words is "eighty-one million, eight hundred ten thousand, one hundred twenty-five".