81101609 has 2 divisors, whose sum is σ = 81101610. Its totient is φ = 81101608.

The previous prime is 81101599. The next prime is 81101621. The reversal of 81101609 is 90610118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 48930025 + 32171584 = 6995^2 + 5672^2 .

It is a cyclic number.

It is not a de Polignac number, because 81101609 - 2⁴ = 81101593 is a prime.

It is not a weakly prime, because it can be changed into another prime (81101689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40550804 + 40550805.

It is an arithmetic number, because the mean of its divisors is an integer number (40550805).

Almost surely, 2^81101609 is an apocalyptic number.

It is an amenable number.

81101609 is a deficient number, since it is larger than the sum of its proper divisors (1).

81101609 is an equidigital number, since it uses as much as digits as its factorization.

81101609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 26.

The square root of 81101609 is about 9005.6431752541. The cubic root of 81101609 is about 432.8557159097.

The spelling of 81101609 in words is "eighty-one million, one hundred one thousand, six hundred nine".