81445021 has 16 divisors (see below), whose sum is σ = 96963840. Its totient is φ = 66931200.

The previous prime is 81444997. The next prime is 81445027. The reversal of 81445021 is 12054418.

It is not a de Polignac number, because 81445021 - 2⁵ = 81444989 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 (81445027) 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, 29325 + ... + 31981.

It is an arithmetic number, because the mean of its divisors is an integer number (6060240).

Almost surely, 2^81445021 is an apocalyptic number.

It is an amenable number.

81445021 is a deficient number, since it is larger than the sum of its proper divisors (15518819).

81445021 is a wasteful number, since it uses less digits than its factorization.

81445021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2844.

The product of its (nonzero) digits is 1280, while the sum is 25.

The square root of 81445021 is about 9024.6895237454. The cubic root of 81445021 is about 433.4658087404.

Adding to 81445021 its reverse (12054418), we get a palindrome (93499439).

The spelling of 81445021 in words is "eighty-one million, four hundred forty-five thousand, twenty-one".