666401235778 has 16 divisors (see below), whose sum is σ = 1000500934176. Its totient is φ = 332900991360.

The previous prime is 666401235763. The next prime is 666401235793. The reversal of 666401235778 is 877532104666.

It is an interprime number because it is at equal distance from previous prime (666401235763) and next prime (666401235793).

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 38909925 + ... + 38927047.

It is an arithmetic number, because the mean of its divisors is an integer number (62531308386).

Almost surely, 2^666401235778 is an apocalyptic number.

666401235778 is a deficient number, since it is larger than the sum of its proper divisors (334099698398).

666401235778 is a wasteful number, since it uses less digits than its factorization.

666401235778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33489.

The product of its (nonzero) digits is 10160640, while the sum is 55.

The spelling of 666401235778 in words is "six hundred sixty-six billion, four hundred one million, two hundred thirty-five thousand, seven hundred seventy-eight".