21256043016511 has 4 divisors (see below), whose sum is σ = 21258114967800. Its totient is φ = 21253971065224.

The previous prime is 21256043016487. The next prime is 21256043016541. The reversal of 21256043016511 is 11561034065212.

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

It is a cyclic number.

It is not a de Polignac number, because 21256043016511 - 2¹⁷ = 21256042885439 is a prime.

It is a super-2 number, since 2×21256043016511² (a number of 27 digits) 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 (21256043016541) 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, 1035960256 + ... + 1035980773.

It is an arithmetic number, because the mean of its divisors is an integer number (5314528741950).

Almost surely, 2^{21256043016511} is an apocalyptic number.

21256043016511 is a deficient number, since it is larger than the sum of its proper divisors (2071951289).

21256043016511 is a wasteful number, since it uses less digits than its factorization.

21256043016511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2071951288.

The product of its (nonzero) digits is 43200, while the sum is 37.

The spelling of 21256043016511 in words is "twenty-one trillion, two hundred fifty-six billion, forty-three million, sixteen thousand, five hundred eleven".