21500054568821 has 2 divisors, whose sum is σ = 21500054568822. Its totient is φ = 21500054568820.

The previous prime is 21500054568761. The next prime is 21500054568823. The reversal of 21500054568821 is 12886545000512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19040254428196 + 2459800140625 = 4363514^2 + 1568375^2 .

It is a cyclic number.

It is not a de Polignac number, because 21500054568821 - 2¹⁸ = 21500054306677 is a prime.

Together with 21500054568823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21500054568823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750027284410 + 10750027284411.

It is an arithmetic number, because the mean of its divisors is an integer number (10750027284411).

Almost surely, 2^{21500054568821} is an apocalyptic number.

It is an amenable number.

21500054568821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21500054568821 is an equidigital number, since it uses as much as digits as its factorization.

21500054568821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 768000, while the sum is 47.

The spelling of 21500054568821 in words is "twenty-one trillion, five hundred billion, fifty-four million, five hundred sixty-eight thousand, eight hundred twenty-one".