81279409 has 2 divisors, whose sum is σ = 81279410. Its totient is φ = 81279408.

The previous prime is 81279391. The next prime is 81279413. The reversal of 81279409 is 90497218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70090384 + 11189025 = 8372^2 + 3345^2 .

It is a cyclic number.

It is not a de Polignac number, because 81279409 - 2⁵ = 81279377 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81279449) 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, 40639704 + 40639705.

It is an arithmetic number, because the mean of its divisors is an integer number (40639705).

Almost surely, 2^81279409 is an apocalyptic number.

It is an amenable number.

81279409 is a deficient number, since it is larger than the sum of its proper divisors (1).

81279409 is an equidigital number, since it uses as much as digits as its factorization.

81279409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 81279409 is about 9015.5093588771. The cubic root of 81279409 is about 433.1718032403.

The spelling of 81279409 in words is "eighty-one million, two hundred seventy-nine thousand, four hundred nine".