405666661 has 2 divisors, whose sum is σ = 405666662. Its totient is φ = 405666660.

The previous prime is 405666637. The next prime is 405666673. The reversal of 405666661 is 166666504.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 324216036 + 81450625 = 18006^2 + 9025^2 .

It is a cyclic number.

It is not a de Polignac number, because 405666661 - 2⁵ = 405666629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (405766661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 202833330 + 202833331.

It is an arithmetic number, because the mean of its divisors is an integer number (202833331).

Almost surely, 2^405666661 is an apocalyptic number.

It is an amenable number.

405666661 is a deficient number, since it is larger than the sum of its proper divisors (1).

405666661 is an equidigital number, since it uses as much as digits as its factorization.

405666661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 155520, while the sum is 40.

The square root of 405666661 is about 20141.1683126873. The cubic root of 405666661 is about 740.2693571416.

The spelling of 405666661 in words is "four hundred five million, six hundred sixty-six thousand, six hundred sixty-one".