255781638 has 80 divisors (see below), whose sum is σ = 666293760. Its totient is φ = 71823024.

The previous prime is 255781637. The next prime is 255781649. The reversal of 255781638 is 836187552.

255781638 is a `hidden beast` number, since 2 + 5 + 5 + 7 + 8 + 1 + 638 = 666.

It is a super-3 number, since 3×255781638³ (a number of 26 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 255781593 and 255781602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (255781633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 64995 + ... + 68817.

It is an arithmetic number, because the mean of its divisors is an integer number (8328672).

Almost surely, 2^255781638 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 255781638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (333146880).

255781638 is an abundant number, since it is smaller than the sum of its proper divisors (410512122).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

255781638 is a wasteful number, since it uses less digits than its factorization.

255781638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3903 (or 3894 counting only the distinct ones).

The product of its digits is 403200, while the sum is 45.

The square root of 255781638 is about 15993.1747317410. The cubic root of 255781638 is about 634.7798339798.

The spelling of 255781638 in words is "two hundred fifty-five million, seven hundred eighty-one thousand, six hundred thirty-eight".