81921389073 has 16 divisors (see below), whose sum is σ = 109386902976. Its totient is φ = 54535127040.

The previous prime is 81921389041. The next prime is 81921389087. The reversal of 81921389073 is 37098312918.

It is not a de Polignac number, because 81921389073 - 2⁵ = 81921389041 is a prime.

It is a super-2 number, since 2×81921389073² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81921389023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6950161 + ... + 6961937.

It is an arithmetic number, because the mean of its divisors is an integer number (6836681436).

Almost surely, 2^81921389073 is an apocalyptic number.

It is an amenable number.

81921389073 is a deficient number, since it is larger than the sum of its proper divisors (27465513903).

81921389073 is a wasteful number, since it uses less digits than its factorization.

81921389073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14944.

The product of its (nonzero) digits is 653184, while the sum is 51.

The spelling of 81921389073 in words is "eighty-one billion, nine hundred twenty-one million, three hundred eighty-nine thousand, seventy-three".