81006821 has 8 divisors (see below), whose sum is σ = 93620160. Its totient is φ = 68653728.

The previous prime is 81006817. The next prime is 81006829. The reversal of 81006821 is 12860018.

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

It is a cyclic number.

It is not a de Polignac number, because 81006821 - 2² = 81006817 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 (81006829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 64391 + ... + 65636.

It is an arithmetic number, because the mean of its divisors is an integer number (11702520).

Almost surely, 2^81006821 is an apocalyptic number.

It is an amenable number.

81006821 is a deficient number, since it is larger than the sum of its proper divisors (12613339).

81006821 is a wasteful number, since it uses less digits than its factorization.

81006821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130123.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 81006821 is about 9000.3789364671. The cubic root of 81006821 is about 432.6870159172.

Adding to 81006821 its reverse (12860018), we get a palindrome (93866839).

The spelling of 81006821 in words is "eighty-one million, six thousand, eight hundred twenty-one".