81992909 has 2 divisors, whose sum is σ = 81992910. Its totient is φ = 81992908.

The previous prime is 81992899. The next prime is 81992927. The reversal of 81992909 is 90929918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81956809 + 36100 = 9053^2 + 190^2 .

It is a cyclic number.

It is not a de Polignac number, because 81992909 - 2⁴ = 81992893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81992929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40996454 + 40996455.

It is an arithmetic number, because the mean of its divisors is an integer number (40996455).

Almost surely, 2^81992909 is an apocalyptic number.

It is an amenable number.

81992909 is a deficient number, since it is larger than the sum of its proper divisors (1).

81992909 is an equidigital number, since it uses as much as digits as its factorization.

81992909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 104976, while the sum is 47.

The square root of 81992909 is about 9054.9935946968. The cubic root of 81992909 is about 434.4356251597.

The spelling of 81992909 in words is "eighty-one million, nine hundred ninety-two thousand, nine hundred nine".