661409471 has 2 divisors, whose sum is σ = 661409472. Its totient is φ = 661409470.

The previous prime is 661409383. The next prime is 661409473. The reversal of 661409471 is 174904166.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661409471 is a prime.

It is a super-3 number, since 3×661409471³ (a number of 27 digits) contains 333 as substring.

Together with 661409473, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661409473) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330704735 + 330704736.

It is an arithmetic number, because the mean of its divisors is an integer number (330704736).

Almost surely, 2^661409471 is an apocalyptic number.

661409471 is a deficient number, since it is larger than the sum of its proper divisors (1).

661409471 is an equidigital number, since it uses as much as digits as its factorization.

661409471 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 38.

The square root of 661409471 is about 25717.8823195068. The cubic root of 661409471 is about 871.2781104084.

The spelling of 661409471 in words is "six hundred sixty-one million, four hundred nine thousand, four hundred seventy-one".