81820101 has 16 divisors (see below), whose sum is σ = 119162880. Its totient is φ = 49524720.

The previous prime is 81820073. The next prime is 81820117. The reversal of 81820101 is 10102818.

It is not a de Polignac number, because 81820101 - 2⁵ = 81820069 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81820121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46626 + ... + 48348.

It is an arithmetic number, because the mean of its divisors is an integer number (7447680).

Almost surely, 2^81820101 is an apocalyptic number.

It is an amenable number.

81820101 is a deficient number, since it is larger than the sum of its proper divisors (37342779).

81820101 is a wasteful number, since it uses less digits than its factorization.

81820101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3176.

The product of its (nonzero) digits is 128, while the sum is 21.

The square root of 81820101 is about 9045.4464234774. The cubic root of 81820101 is about 434.1302054344.

Adding to 81820101 its reverse (10102818), we get a palindrome (91922919).

The spelling of 81820101 in words is "eighty-one million, eight hundred twenty thousand, one hundred one".