81929321 has 4 divisors (see below), whose sum is σ = 84754500. Its totient is φ = 79104144.

The previous prime is 81929303. The next prime is 81929329. The reversal of 81929321 is 12392918.

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 13039321 + 68890000 = 3611^2 + 8300^2 .

It is a cyclic number.

It is not a de Polignac number, because 81929321 - 2⁶ = 81929257 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81929329) 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, 1412546 + ... + 1412603.

It is an arithmetic number, because the mean of its divisors is an integer number (21188625).

Almost surely, 2^81929321 is an apocalyptic number.

It is an amenable number.

81929321 is a deficient number, since it is larger than the sum of its proper divisors (2825179).

81929321 is a wasteful number, since it uses less digits than its factorization.

81929321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2825178.

The product of its digits is 7776, while the sum is 35.

The square root of 81929321 is about 9051.4817019094. The cubic root of 81929321 is about 434.3232900921.

The spelling of 81929321 in words is "eighty-one million, nine hundred twenty-nine thousand, three hundred twenty-one".