256623317424721 has 4 divisors (see below), whose sum is σ = 276363572611252. Its totient is φ = 236883062238192.

The previous prime is 256623317424707. The next prime is 256623317424757. The reversal of 256623317424721 is 127424713326652.

It is a happy number.

256623317424721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 81209583396496 + 175413734028225 = 9011636^2 + 13244385^2 .

It is a cyclic number.

It is not a de Polignac number, because 256623317424721 - 2¹⁵ = 256623317391953 is a prime.

It is a super-2 number, since 2×256623317424721² (a number of 30 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256623317424781) 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, 9870127593246 + ... + 9870127593271.

It is an arithmetic number, because the mean of its divisors is an integer number (69090893152813).

Almost surely, 2^{256623317424721} is an apocalyptic number.

It is an amenable number.

256623317424721 is a deficient number, since it is larger than the sum of its proper divisors (19740255186531).

256623317424721 is a wasteful number, since it uses less digits than its factorization.

256623317424721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19740255186530.

The product of its digits is 20321280, while the sum is 55.

The spelling of 256623317424721 in words is "two hundred fifty-six trillion, six hundred twenty-three billion, three hundred seventeen million, four hundred twenty-four thousand, seven hundred twenty-one".