81197973 has 18 divisors (see below), whose sum is σ = 118984866. Its totient is φ = 53358912.

The previous prime is 81197957. The next prime is 81197989. The reversal of 81197973 is 37979118.

It is an interprime number because it is at equal distance from previous prime (81197957) and next prime (81197989).

It can be written as a sum of positive squares in 3 ways, for example, as 12341169 + 68856804 = 3513^2 + 8298^2 .

It is not a de Polignac number, because 81197973 - 2⁴ = 81197957 is a prime.

It is a super-2 number, since 2×81197973² = 13186221638617458, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81197953) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 47115 + ... + 48807.

Almost surely, 2^81197973 is an apocalyptic number.

It is an amenable number.

81197973 is a deficient number, since it is larger than the sum of its proper divisors (37786893).

81197973 is a wasteful number, since it uses less digits than its factorization.

81197973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1845 (or 1769 counting only the distinct ones).

The product of its digits is 95256, while the sum is 45.

The square root of 81197973 is about 9010.9917878112. The cubic root of 81197973 is about 433.0270861170.

The spelling of 81197973 in words is "eighty-one million, one hundred ninety-seven thousand, nine hundred seventy-three".