81799971 has 32 divisors (see below), whose sum is σ = 127008000. Its totient is φ = 46279680.

The previous prime is 81799897. The next prime is 81799973. The reversal of 81799971 is 17999718.

It is not a de Polignac number, because 81799971 - 2¹⁰ = 81798947 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is not an unprimeable number, because it can be changed into a prime (81799973) 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 31 ways as a sum of consecutive naturals, for example, 77455 + ... + 78503.

It is an arithmetic number, because the mean of its divisors is an integer number (3969000).

Almost surely, 2^81799971 is an apocalyptic number.

81799971 is a deficient number, since it is larger than the sum of its proper divisors (45208029).

81799971 is a wasteful number, since it uses less digits than its factorization.

81799971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1219.

The product of its digits is 285768, while the sum is 51.

The square root of 81799971 is about 9044.3336404624. Note that the first 3 decimals coincide. The cubic root of 81799971 is about 434.0945998488.

The spelling of 81799971 in words is "eighty-one million, seven hundred ninety-nine thousand, nine hundred seventy-one".