81168421 has 4 divisors (see below), whose sum is σ = 85943052. Its totient is φ = 76393792.

The previous prime is 81168413. The next prime is 81168431. The reversal of 81168421 is 12486118.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 68707521 + 12460900 = 8289^2 + 3530^2 .

It is a cyclic number.

It is not a de Polignac number, because 81168421 - 2³ = 81168413 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 (81168401) 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 3 ways as a sum of consecutive naturals, for example, 2387290 + ... + 2387323.

It is an arithmetic number, because the mean of its divisors is an integer number (21485763).

Almost surely, 2^81168421 is an apocalyptic number.

It is an amenable number.

81168421 is a deficient number, since it is larger than the sum of its proper divisors (4774631).

81168421 is a wasteful number, since it uses less digits than its factorization.

81168421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4774630.

The product of its digits is 3072, while the sum is 31.

The square root of 81168421 is about 9009.3518634805. The cubic root of 81168421 is about 432.9745463439.

The spelling of 81168421 in words is "eighty-one million, one hundred sixty-eight thousand, four hundred twenty-one".