21553555204477 has 2 divisors, whose sum is σ = 21553555204478. Its totient is φ = 21553555204476.

The previous prime is 21553555204393. The next prime is 21553555204501. The reversal of 21553555204477 is 77440255535512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18930383020836 + 2623172183641 = 4350906^2 + 1619621^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21553555204477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21553555264477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10776777602238 + 10776777602239.

It is an arithmetic number, because the mean of its divisors is an integer number (10776777602239).

Almost surely, 2^{21553555204477} is an apocalyptic number.

It is an amenable number.

21553555204477 is a deficient number, since it is larger than the sum of its proper divisors (1).

21553555204477 is an equidigital number, since it uses as much as digits as its factorization.

21553555204477 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 29400000, while the sum is 55.

The spelling of 21553555204477 in words is "twenty-one trillion, five hundred fifty-three billion, five hundred fifty-five million, two hundred four thousand, four hundred seventy-seven".