21408881260777 has 2 divisors, whose sum is σ = 21408881260778. Its totient is φ = 21408881260776.

The previous prime is 21408881260651. The next prime is 21408881260841. The reversal of 21408881260777 is 77706218880412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13791634536681 + 7617246724096 = 3713709^2 + 2759936^2 .

It is a cyclic number.

It is not a de Polignac number, because 21408881260777 - 2³¹ = 21406733777129 is a prime.

It is not a weakly prime, because it can be changed into another prime (21408881266777) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704440630388 + 10704440630389.

It is an arithmetic number, because the mean of its divisors is an integer number (10704440630389).

Almost surely, 2^{21408881260777} is an apocalyptic number.

It is an amenable number.

21408881260777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408881260777 is an equidigital number, since it uses as much as digits as its factorization.

21408881260777 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16859136, while the sum is 61.

The spelling of 21408881260777 in words is "twenty-one trillion, four hundred eight billion, eight hundred eighty-one million, two hundred sixty thousand, seven hundred seventy-seven".