621553444209877 has 2 divisors, whose sum is σ = 621553444209878. Its totient is φ = 621553444209876.

The previous prime is 621553444209829. The next prime is 621553444209883. The reversal of 621553444209877 is 778902444355126.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 424381465471441 + 197171978738436 = 20600521^2 + 14041794^2 .

It is a cyclic number.

It is not a de Polignac number, because 621553444209877 - 2¹⁹ = 621553443685589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (621553444209977) 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 as a sum of consecutive naturals, namely, 310776722104938 + 310776722104939.

It is an arithmetic number, because the mean of its divisors is an integer number (310776722104939).

It is a 2-persistent number, because it is pandigital, and so is 2⋅621553444209877 = 1243106888419754, but 3⋅621553444209877 = 1864660332629631 is not.

Almost surely, 2^{621553444209877} is an apocalyptic number.

It is an amenable number.

621553444209877 is a deficient number, since it is larger than the sum of its proper divisors (1).

621553444209877 is an equidigital number, since it uses as much as digits as its factorization.

621553444209877 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 406425600, while the sum is 67.

The spelling of 621553444209877 in words is "six hundred twenty-one trillion, five hundred fifty-three billion, four hundred forty-four million, two hundred nine thousand, eight hundred seventy-seven".