81638153 has 4 divisors (see below), whose sum is σ = 81688068. Its totient is φ = 81588240.

The previous prime is 81638147. The next prime is 81638173. The reversal of 81638153 is 35183618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 35183618 = 2 ⋅17591809.

It can be written as a sum of positive squares in 2 ways, for example, as 14348944 + 67289209 = 3788^2 + 8203^2 .

It is a cyclic number.

It is not a de Polignac number, because 81638153 - 2¹² = 81634057 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81638113) 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, 22418 + ... + 25803.

It is an arithmetic number, because the mean of its divisors is an integer number (20422017).

Almost surely, 2^81638153 is an apocalyptic number.

It is an amenable number.

81638153 is a deficient number, since it is larger than the sum of its proper divisors (49915).

81638153 is a wasteful number, since it uses less digits than its factorization.

81638153 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49914.

The product of its digits is 17280, while the sum is 35.

The square root of 81638153 is about 9035.3833897627. The cubic root of 81638153 is about 433.8081666160.

The spelling of 81638153 in words is "eighty-one million, six hundred thirty-eight thousand, one hundred fifty-three".