661353788213666 has 8 divisors (see below), whose sum is σ = 1010748242364444. Its totient is φ = 324437707425520.

The previous prime is 661353788213617. The next prime is 661353788213669. The reversal of 661353788213666 is 666312887353166.

It can be written as a sum of positive squares in 2 ways, for example, as 649125681423025 + 12228106790641 = 25477945^2 + 3496871^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 661353788213666.

It is not an unprimeable number, because it can be changed into a prime (661353788213669) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3119593340525 + ... + 3119593340736.

Almost surely, 2^{661353788213666} is an apocalyptic number.

661353788213666 is a deficient number, since it is larger than the sum of its proper divisors (349394454150778).

661353788213666 is a wasteful number, since it uses less digits than its factorization.

661353788213666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6239186681316.

The product of its digits is 940584960, while the sum is 71.

The spelling of 661353788213666 in words is "six hundred sixty-one trillion, three hundred fifty-three billion, seven hundred eighty-eight million, two hundred thirteen thousand, six hundred sixty-six".