81143749 has 2 divisors, whose sum is σ = 81143750. Its totient is φ = 81143748.

The previous prime is 81143731. The next prime is 81143759. The reversal of 81143749 is 94734118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74943649 + 6200100 = 8657^2 + 2490^2 .

It is a cyclic number.

It is not a de Polignac number, because 81143749 - 2¹³ = 81135557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81143719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40571874 + 40571875.

It is an arithmetic number, because the mean of its divisors is an integer number (40571875).

Almost surely, 2^81143749 is an apocalyptic number.

It is an amenable number.

81143749 is a deficient number, since it is larger than the sum of its proper divisors (1).

81143749 is an equidigital number, since it uses as much as digits as its factorization.

81143749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 37.

The square root of 81143749 is about 9007.9825155248. The cubic root of 81143749 is about 432.9306728342.

The spelling of 81143749 in words is "eighty-one million, one hundred forty-three thousand, seven hundred forty-nine".