256684166991 has 12 divisors (see below), whose sum is σ = 423732593232. Its totient is φ = 146676666816.

The previous prime is 256684166987. The next prime is 256684167029. The reversal of 256684166991 is 199661486652.

256684166991 is a `hidden beast` number, since 2 + 566 + 8 + 4 + 1 + 6 + 69 + 9 + 1 = 666.

It is not a de Polignac number, because 256684166991 - 2² = 256684166987 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (63), and also a Moran number because the ratio is a prime number: 4074351857 = 256684166991 / (2 + 5 + 6 + 6 + 8 + 4 + 1 + 6 + 6 + 9 + 9 + 1).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256684166911) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2037175866 + ... + 2037175991.

It is an arithmetic number, because the mean of its divisors is an integer number (35311049436).

Almost surely, 2^256684166991 is an apocalyptic number.

256684166991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

256684166991 is a deficient number, since it is larger than the sum of its proper divisors (167048426241).

256684166991 is a wasteful number, since it uses less digits than its factorization.

256684166991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4074351870 (or 4074351867 counting only the distinct ones).

The product of its digits is 33592320, while the sum is 63.

The spelling of 256684166991 in words is "two hundred fifty-six billion, six hundred eighty-four million, one hundred sixty-six thousand, nine hundred ninety-one".