81751231 has 2 divisors, whose sum is σ = 81751232. Its totient is φ = 81751230.

The previous prime is 81751193. The next prime is 81751237. The reversal of 81751231 is 13215718.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81751231 is a prime.

It is a super-2 number, since 2×81751231² = 13366527540030722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81751231.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81751237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40875615 + 40875616.

It is an arithmetic number, because the mean of its divisors is an integer number (40875616).

Almost surely, 2^81751231 is an apocalyptic number.

81751231 is a deficient number, since it is larger than the sum of its proper divisors (1).

81751231 is an equidigital number, since it uses as much as digits as its factorization.

81751231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 28.

The square root of 81751231 is about 9041.6387342118. The cubic root of 81751231 is about 434.0083652036.

Adding to 81751231 its reverse (13215718), we get a palindrome (94966949).

The spelling of 81751231 in words is "eighty-one million, seven hundred fifty-one thousand, two hundred thirty-one".