256721397 has 8 divisors (see below), whose sum is σ = 342438240. Its totient is φ = 171076080.

The previous prime is 256721393. The next prime is 256721411. The reversal of 256721397 is 793127652.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 256721397 - 2² = 256721393 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256721393) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8854 + ... + 24327.

It is an arithmetic number, because the mean of its divisors is an integer number (42804780).

Almost surely, 2^256721397 is an apocalyptic number.

It is an amenable number.

256721397 is a deficient number, since it is larger than the sum of its proper divisors (85716843).

256721397 is a wasteful number, since it uses less digits than its factorization.

256721397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35763.

The product of its digits is 158760, while the sum is 42.

The square root of 256721397 is about 16022.5277968241. The cubic root of 256721397 is about 635.5562918184.

The spelling of 256721397 in words is "two hundred fifty-six million, seven hundred twenty-one thousand, three hundred ninety-seven".