81500641 has 2 divisors, whose sum is σ = 81500642. Its totient is φ = 81500640.

The previous prime is 81500623. The next prime is 81500647. The reversal of 81500641 is 14600518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 67174416 + 14326225 = 8196^2 + 3785^2 .

It is a cyclic number.

It is not a de Polignac number, because 81500641 - 2⁷ = 81500513 is a prime.

It is not a weakly prime, because it can be changed into another prime (81500647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40750320 + 40750321.

It is an arithmetic number, because the mean of its divisors is an integer number (40750321).

Almost surely, 2^81500641 is an apocalyptic number.

It is an amenable number.

81500641 is a deficient number, since it is larger than the sum of its proper divisors (1).

81500641 is an equidigital number, since it uses as much as digits as its factorization.

81500641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 81500641 is about 9027.7705442706. The cubic root of 81500641 is about 433.5644596743.

The spelling of 81500641 in words is "eighty-one million, five hundred thousand, six hundred forty-one".