81327209 has 2 divisors, whose sum is σ = 81327210. Its totient is φ = 81327208.

The previous prime is 81327187. The next prime is 81327251. The reversal of 81327209 is 90272318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 46280809 + 35046400 = 6803^2 + 5920^2 .

It is a cyclic number.

It is not a de Polignac number, because 81327209 - 2⁸ = 81326953 is a prime.

It is a super-2 number, since 2×81327209² = 13228229847459362, which contains 22 as substring.

It is equal to p_4742465 and since 81327209 and 4742465 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81327299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40663604 + 40663605.

It is an arithmetic number, because the mean of its divisors is an integer number (40663605).

Almost surely, 2^81327209 is an apocalyptic number.

It is an amenable number.

81327209 is a deficient number, since it is larger than the sum of its proper divisors (1).

81327209 is an equidigital number, since it uses as much as digits as its factorization.

81327209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 81327209 is about 9018.1599564434. The cubic root of 81327209 is about 433.2567019653.

The spelling of 81327209 in words is "eighty-one million, three hundred twenty-seven thousand, two hundred nine".