81231757 has 2 divisors, whose sum is σ = 81231758. Its totient is φ = 81231756.

The previous prime is 81231751. The next prime is 81231767. The reversal of 81231757 is 75713218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65383396 + 15848361 = 8086^2 + 3981^2 .

It is a cyclic number.

It is not a de Polignac number, because 81231757 - 2⁷ = 81231629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81231751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40615878 + 40615879.

It is an arithmetic number, because the mean of its divisors is an integer number (40615879).

Almost surely, 2^81231757 is an apocalyptic number.

It is an amenable number.

81231757 is a deficient number, since it is larger than the sum of its proper divisors (1).

81231757 is an equidigital number, since it uses as much as digits as its factorization.

81231757 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11760, while the sum is 34.

The square root of 81231757 is about 9012.8661922831. The cubic root of 81231757 is about 433.0871342440.

The spelling of 81231757 in words is "eighty-one million, two hundred thirty-one thousand, seven hundred fifty-seven".