81605101 has 4 divisors (see below), whose sum is σ = 84419100. Its totient is φ = 78791104.

The previous prime is 81605089. The next prime is 81605123. The reversal of 81605101 is 10150618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 10150618 = 2 ⋅5075309.

It can be written as a sum of positive squares in 2 ways, for example, as 62015625 + 19589476 = 7875^2 + 4426^2 .

It is a cyclic number.

It is not a de Polignac number, because 81605101 - 2⁷ = 81604973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81605131) 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, 1406956 + ... + 1407013.

It is an arithmetic number, because the mean of its divisors is an integer number (21104775).

Almost surely, 2^81605101 is an apocalyptic number.

It is an amenable number.

81605101 is a deficient number, since it is larger than the sum of its proper divisors (2813999).

81605101 is a wasteful number, since it uses less digits than its factorization.

81605101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2813998.

The product of its (nonzero) digits is 240, while the sum is 22.

The square root of 81605101 is about 9033.5541731923. The cubic root of 81605101 is about 433.7496148956.

Adding to 81605101 its reverse (10150618), we get a palindrome (91755719).

The spelling of 81605101 in words is "eighty-one million, six hundred five thousand, one hundred one".