256809720 has 64 divisors (see below), whose sum is σ = 803934720. Its totient is φ = 65504384.

The previous prime is 256809659. The next prime is 256809781. The reversal of 256809720 is 27908652.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (256809659) and next prime (256809781).

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 43764 + ... + 49283.

It is an arithmetic number, because the mean of its divisors is an integer number (12561480).

Almost surely, 2^256809720 is an apocalyptic number.

256809720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

256809720 is an abundant number, since it is smaller than the sum of its proper divisors (547125000).

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

256809720 is a wasteful number, since it uses less digits than its factorization.

256809720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93084 (or 93080 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 39.

The square root of 256809720 is about 16025.2837728385. The cubic root of 256809720 is about 635.6291695278.

The spelling of 256809720 in words is "two hundred fifty-six million, eight hundred nine thousand, seven hundred twenty".