665455409 has 2 divisors, whose sum is σ = 665455410. Its totient is φ = 665455408.

The previous prime is 665455321. The next prime is 665455423. The reversal of 665455409 is 904554566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 662805025 + 2650384 = 25745^2 + 1628^2 .

It is a cyclic number.

It is not a de Polignac number, because 665455409 - 2²⁰ = 664406833 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 665455409.

It is not a weakly prime, because it can be changed into another prime (665415409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332727704 + 332727705.

It is an arithmetic number, because the mean of its divisors is an integer number (332727705).

Almost surely, 2^665455409 is an apocalyptic number.

It is an amenable number.

665455409 is a deficient number, since it is larger than the sum of its proper divisors (1).

665455409 is an equidigital number, since it uses as much as digits as its factorization.

665455409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648000, while the sum is 44.

The square root of 665455409 is about 25796.4224069928. The cubic root of 665455409 is about 873.0510784775.

The spelling of 665455409 in words is "six hundred sixty-five million, four hundred fifty-five thousand, four hundred nine".