81513125 has 20 divisors (see below), whose sum is σ = 104375964. Its totient is φ = 63600000.

The previous prime is 81513121. The next prime is 81513137. The reversal of 81513125 is 52131518.

It is a happy number.

It can be written as a sum of positive squares in 10 ways, for example, as 81414529 + 98596 = 9023^2 + 314^2 .

It is not a de Polignac number, because 81513125 - 2² = 81513121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81513094 and 81513103.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81513121) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 24035 + ... + 27215.

Almost surely, 2^81513125 is an apocalyptic number.

It is an amenable number.

81513125 is a deficient number, since it is larger than the sum of its proper divisors (22862839).

81513125 is an equidigital number, since it uses as much as digits as its factorization.

81513125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3242 (or 3227 counting only the distinct ones).

The product of its digits is 1200, while the sum is 26.

The square root of 81513125 is about 9028.4619398877. The cubic root of 81513125 is about 433.5865958698.

The spelling of 81513125 in words is "eighty-one million, five hundred thirteen thousand, one hundred twenty-five".