256929781 has 4 divisors (see below), whose sum is σ = 257012064. Its totient is φ = 256847500.

The previous prime is 256929779. The next prime is 256929809. The reversal of 256929781 is 187929652.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 256929781 - 2¹ = 256929779 is a prime.

It is a super-2 number, since 2×256929781² = 132025824729415922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256929181) 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, 36265 + ... + 42766.

It is an arithmetic number, because the mean of its divisors is an integer number (64253016).

Almost surely, 2^256929781 is an apocalyptic number.

It is an amenable number.

256929781 is a deficient number, since it is larger than the sum of its proper divisors (82283).

256929781 is an equidigital number, since it uses as much as digits as its factorization.

256929781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82282.

The product of its digits is 544320, while the sum is 49.

The square root of 256929781 is about 16029.0293218273. The cubic root of 256929781 is about 635.7282083340.

The spelling of 256929781 in words is "two hundred fifty-six million, nine hundred twenty-nine thousand, seven hundred eighty-one".