81973519 has 4 divisors (see below), whose sum is σ = 82785240. Its totient is φ = 81161800.

The previous prime is 81973501. The next prime is 81973561. The reversal of 81973519 is 91537918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 91537918 = 2 ⋅45768959.

It is a cyclic number.

It is not a de Polignac number, because 81973519 - 2¹³ = 81965327 is a prime.

It is a super-2 number, since 2×81973519² = 13439315634486722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81973319) 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, 405709 + ... + 405910.

It is an arithmetic number, because the mean of its divisors is an integer number (20696310).

Almost surely, 2^81973519 is an apocalyptic number.

81973519 is a deficient number, since it is larger than the sum of its proper divisors (811721).

81973519 is a wasteful number, since it uses less digits than its factorization.

81973519 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 811720.

The product of its digits is 68040, while the sum is 43.

The square root of 81973519 is about 9053.9228514495. The cubic root of 81973519 is about 434.4013767879.

The spelling of 81973519 in words is "eighty-one million, nine hundred seventy-three thousand, five hundred nineteen".