81129731 has 2 divisors, whose sum is σ = 81129732. Its totient is φ = 81129730.

The previous prime is 81129703. The next prime is 81129751. The reversal of 81129731 is 13792118.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81129731 is a prime.

It is a super-2 number, since 2×81129731² = 13164066504264722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81129751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40564865 + 40564866.

It is an arithmetic number, because the mean of its divisors is an integer number (40564866).

Almost surely, 2^81129731 is an apocalyptic number.

81129731 is a deficient number, since it is larger than the sum of its proper divisors (1).

81129731 is an equidigital number, since it uses as much as digits as its factorization.

81129731 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 32.

The square root of 81129731 is about 9007.2043942613. The cubic root of 81129731 is about 432.9057410649.

The spelling of 81129731 in words is "eighty-one million, one hundred twenty-nine thousand, seven hundred thirty-one".