81465821 has 4 divisors (see below), whose sum is σ = 81484032. Its totient is φ = 81447612.

The previous prime is 81465809. The next prime is 81465829. The reversal of 81465821 is 12856418.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81465821 - 2⁶ = 81465757 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 (81465829) 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, 2756 + ... + 13058.

It is an arithmetic number, because the mean of its divisors is an integer number (20371008).

Almost surely, 2^81465821 is an apocalyptic number.

It is an amenable number.

81465821 is a deficient number, since it is larger than the sum of its proper divisors (18211).

81465821 is a wasteful number, since it uses less digits than its factorization.

81465821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18210.

The product of its digits is 15360, while the sum is 35.

The square root of 81465821 is about 9025.8418443932. The cubic root of 81465821 is about 433.5027061111.

The spelling of 81465821 in words is "eighty-one million, four hundred sixty-five thousand, eight hundred twenty-one".