81538685 has 16 divisors (see below), whose sum is σ = 100018800. Its totient is φ = 63799296.

The previous prime is 81538669. The next prime is 81538687. The reversal of 81538685 is 58683518.

It can be written as a sum of positive squares in 8 ways, for example, as 5866084 + 75672601 = 2422^2 + 8699^2 .

It is a cyclic number.

It is not a de Polignac number, because 81538685 - 2⁴ = 81538669 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81538687) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42221 + ... + 44109.

It is an arithmetic number, because the mean of its divisors is an integer number (6251175).

Almost surely, 2^81538685 is an apocalyptic number.

It is an amenable number.

81538685 is a deficient number, since it is larger than the sum of its proper divisors (18480115).

81538685 is a wasteful number, since it uses less digits than its factorization.

81538685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2080.

The product of its digits is 230400, while the sum is 44.

The square root of 81538685 is about 9029.8773524340. The cubic root of 81538685 is about 433.6319109248.

The spelling of 81538685 in words is "eighty-one million, five hundred thirty-eight thousand, six hundred eighty-five".