81924121 has 4 divisors (see below), whose sum is σ = 82336000. Its totient is φ = 81512244.

The previous prime is 81924119. The next prime is 81924127. The reversal of 81924121 is 12142918.

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 81924121 - 2¹ = 81924119 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81924121.

It is not an unprimeable number, because it can be changed into a prime (81924127) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 205641 + ... + 206038.

It is an arithmetic number, because the mean of its divisors is an integer number (20584000).

Almost surely, 2^81924121 is an apocalyptic number.

It is an amenable number.

81924121 is a deficient number, since it is larger than the sum of its proper divisors (411879).

81924121 is a wasteful number, since it uses less digits than its factorization.

81924121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 411878.

The product of its digits is 1152, while the sum is 28.

The square root of 81924121 is about 9051.1944515627. The cubic root of 81924121 is about 434.3141011600.

The spelling of 81924121 in words is "eighty-one million, nine hundred twenty-four thousand, one hundred twenty-one".