81131173 has 2 divisors, whose sum is σ = 81131174. Its totient is φ = 81131172.

The previous prime is 81131147. The next prime is 81131177. The reversal of 81131173 is 37113118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80586529 + 544644 = 8977^2 + 738^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81131173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81131177) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40565586 + 40565587.

It is an arithmetic number, because the mean of its divisors is an integer number (40565587).

Almost surely, 2^81131173 is an apocalyptic number.

It is an amenable number.

81131173 is a deficient number, since it is larger than the sum of its proper divisors (1).

81131173 is an equidigital number, since it uses as much as digits as its factorization.

81131173 is an evil number, because the sum of its binary digits is even.

The product of its digits is 504, while the sum is 25.

The square root of 81131173 is about 9007.2844409400. The cubic root of 81131173 is about 432.9083058722.

The spelling of 81131173 in words is "eighty-one million, one hundred thirty-one thousand, one hundred seventy-three".