81804121 has 4 divisors (see below), whose sum is σ = 93490432. Its totient is φ = 70117812.

The previous prime is 81804113. The next prime is 81804127. The reversal of 81804121 is 12140818.

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 81804121 - 2³ = 81804113 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81804127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5843145 + ... + 5843158.

It is an arithmetic number, because the mean of its divisors is an integer number (23372608).

Almost surely, 2^81804121 is an apocalyptic number.

It is an amenable number.

81804121 is a deficient number, since it is larger than the sum of its proper divisors (11686311).

81804121 is a wasteful number, since it uses less digits than its factorization.

81804121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11686310.

The product of its (nonzero) digits is 512, while the sum is 25.

The square root of 81804121 is about 9044.5630629677. The cubic root of 81804121 is about 434.1019407729.

Adding to 81804121 its reverse (12140818), we get a palindrome (93944939).

The spelling of 81804121 in words is "eighty-one million, eight hundred four thousand, one hundred twenty-one".