81427821 has 8 divisors (see below), whose sum is σ = 108612960. Its totient is φ = 54263952.

The previous prime is 81427817. The next prime is 81427831. The reversal of 81427821 is 12872418.

It is a happy number.

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

It is not a de Polignac number, because 81427821 - 2² = 81427817 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81427831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9591 + ... + 15963.

It is an arithmetic number, because the mean of its divisors is an integer number (13576620).

Almost surely, 2^81427821 is an apocalyptic number.

It is an amenable number.

81427821 is a deficient number, since it is larger than the sum of its proper divisors (27185139).

81427821 is a wasteful number, since it uses less digits than its factorization.

81427821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10635.

The product of its digits is 7168, while the sum is 33.

The square root of 81427821 is about 9023.7365320581. The cubic root of 81427821 is about 433.4352927075.

The spelling of 81427821 in words is "eighty-one million, four hundred twenty-seven thousand, eight hundred twenty-one".