21256043013365 has 16 divisors (see below), whose sum is σ = 25534152205056. Its totient is φ = 16986909777600.

The previous prime is 21256043013329. The next prime is 21256043013367. The reversal of 21256043013365 is 56331034065212.

It is not a de Polignac number, because 21256043013365 - 2²⁰ = 21256041964789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256043013367) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18200135 + ... + 19332795.

It is an arithmetic number, because the mean of its divisors is an integer number (1595884512816).

Almost surely, 2^{21256043013365} is an apocalyptic number.

It is an amenable number.

21256043013365 is a deficient number, since it is larger than the sum of its proper divisors (4278109191691).

21256043013365 is a wasteful number, since it uses less digits than its factorization.

21256043013365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1136620.

The product of its (nonzero) digits is 388800, while the sum is 41.

Adding to 21256043013365 its reverse (56331034065212), we get a palindrome (77587077078577).

The spelling of 21256043013365 in words is "twenty-one trillion, two hundred fifty-six billion, forty-three million, thirteen thousand, three hundred sixty-five".