81823821 has 8 divisors (see below), whose sum is σ = 109752384. Its totient is φ = 54222240.

The previous prime is 81823813. The next prime is 81823831. The reversal of 81823821 is 12832818.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81823821 - 2³ = 81823813 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81823831) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 81160 + ... + 82161.

It is an arithmetic number, because the mean of its divisors is an integer number (13719048).

Almost surely, 2^81823821 is an apocalyptic number.

It is an amenable number.

81823821 is a deficient number, since it is larger than the sum of its proper divisors (27928563).

81823821 is a wasteful number, since it uses less digits than its factorization.

81823821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163491.

The product of its digits is 6144, while the sum is 33.

The square root of 81823821 is about 9045.6520494655. The cubic root of 81823821 is about 434.1367846648.

The spelling of 81823821 in words is "eighty-one million, eight hundred twenty-three thousand, eight hundred twenty-one".