256401205666 has 8 divisors (see below), whose sum is σ = 384632256960. Its totient is φ = 128190453348.

The previous prime is 256401205649. The next prime is 256401205667. The reversal of 256401205666 is 666502104652.

It is a happy number.

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

It is not an unprimeable number, because it can be changed into a prime (256401205667) 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, 5043126 + ... + 5093713.

It is an arithmetic number, because the mean of its divisors is an integer number (48079032120).

Almost surely, 2^256401205666 is an apocalyptic number.

256401205666 is a deficient number, since it is larger than the sum of its proper divisors (128231051294).

256401205666 is a wasteful number, since it uses less digits than its factorization.

256401205666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10149488.

The product of its (nonzero) digits is 518400, while the sum is 43.

The spelling of 256401205666 in words is "two hundred fifty-six billion, four hundred one million, two hundred five thousand, six hundred sixty-six".