81544909 has 2 divisors, whose sum is σ = 81544910. Its totient is φ = 81544908.

The previous prime is 81544889. The next prime is 81544919. The reversal of 81544909 is 90944518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58293225 + 23251684 = 7635^2 + 4822^2 .

It is a cyclic number.

It is not a de Polignac number, because 81544909 - 2⁵ = 81544877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81544919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40772454 + 40772455.

It is an arithmetic number, because the mean of its divisors is an integer number (40772455).

Almost surely, 2^81544909 is an apocalyptic number.

It is an amenable number.

81544909 is a deficient number, since it is larger than the sum of its proper divisors (1).

81544909 is an equidigital number, since it uses as much as digits as its factorization.

81544909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81544909 is about 9030.2219795529. The cubic root of 81544909 is about 433.6429439551.

The spelling of 81544909 in words is "eighty-one million, five hundred forty-four thousand, nine hundred nine".