256623313660666 has 4 divisors (see below), whose sum is σ = 384934970491002. Its totient is φ = 128311656830332.

The previous prime is 256623313660657. The next prime is 256623313660699. The reversal of 256623313660666 is 666066313326652.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 189981316123641 + 66641997537025 = 13783371^2 + 8163455^2 .

It is a super-2 number, since 2×256623313660666² (a number of 30 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64155828415165 + ... + 64155828415168.

Almost surely, 2^{256623313660666} is an apocalyptic number.

256623313660666 is a deficient number, since it is larger than the sum of its proper divisors (128311656830336).

256623313660666 is a wasteful number, since it uses less digits than its factorization.

256623313660666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128311656830335.

The product of its (nonzero) digits is 151165440, while the sum is 61.

The spelling of 256623313660666 in words is "two hundred fifty-six trillion, six hundred twenty-three billion, three hundred thirteen million, six hundred sixty thousand, six hundred sixty-six".