21256063014661 has 4 divisors (see below), whose sum is σ = 21263903689824. Its totient is φ = 21248222339500.

The previous prime is 21256063014649. The next prime is 21256063014701. The reversal of 21256063014661 is 16641036065212.

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 21256063014661 - 2⁵ = 21256063014629 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 (21256063014961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3920333515 + ... + 3920338936.

It is an arithmetic number, because the mean of its divisors is an integer number (5315975922456).

Almost surely, 2^{21256063014661} is an apocalyptic number.

It is an amenable number.

21256063014661 is a deficient number, since it is larger than the sum of its proper divisors (7840675163).

21256063014661 is an equidigital number, since it uses as much as digits as its factorization.

21256063014661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7840675162.

The product of its (nonzero) digits is 311040, while the sum is 43.

Adding to 21256063014661 its reverse (16641036065212), we get a palindrome (37897099079873).

The spelling of 21256063014661 in words is "twenty-one trillion, two hundred fifty-six billion, sixty-three million, fourteen thousand, six hundred sixty-one".