81997473 has 4 divisors (see below), whose sum is σ = 109329968. Its totient is φ = 54664980.

The previous prime is 81997463. The next prime is 81997523. The reversal of 81997473 is 37479918.

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 not a de Polignac number, because 81997473 - 2⁵ = 81997441 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81997453) 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, 13666243 + ... + 13666248.

It is an arithmetic number, because the mean of its divisors is an integer number (27332492).

Almost surely, 2^81997473 is an apocalyptic number.

It is an amenable number.

81997473 is a deficient number, since it is larger than the sum of its proper divisors (27332495).

81997473 is a wasteful number, since it uses less digits than its factorization.

81997473 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27332494.

The product of its digits is 381024, while the sum is 48.

The square root of 81997473 is about 9055.2456068292. The cubic root of 81997473 is about 434.4436857242.

The spelling of 81997473 in words is "eighty-one million, nine hundred ninety-seven thousand, four hundred seventy-three".