81231751 has 2 divisors, whose sum is σ = 81231752. Its totient is φ = 81231750.

The previous prime is 81231743. The next prime is 81231757. The reversal of 81231751 is 15713218.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81231751 - 2³ = 81231743 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81231757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40615875 + 40615876.

It is an arithmetic number, because the mean of its divisors is an integer number (40615876).

Almost surely, 2^81231751 is an apocalyptic number.

81231751 is a deficient number, since it is larger than the sum of its proper divisors (1).

81231751 is an equidigital number, since it uses as much as digits as its factorization.

81231751 is an evil number, because the sum of its binary digits is even.

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

The square root of 81231751 is about 9012.8658594256. The cubic root of 81231751 is about 433.0871235810.

Adding to 81231751 its reverse (15713218), we get a palindrome (96944969).

The spelling of 81231751 in words is "eighty-one million, two hundred thirty-one thousand, seven hundred fifty-one".