21518647454977 has 2 divisors, whose sum is σ = 21518647454978. Its totient is φ = 21518647454976.

The previous prime is 21518647454911. The next prime is 21518647455029. The reversal of 21518647454977 is 77945474681512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11298196515841 + 10220450939136 = 3361279^2 + 3196944^2 .

It is a cyclic number.

It is not a de Polignac number, because 21518647454977 - 2¹⁹ = 21518646930689 is a prime.

It is not a weakly prime, because it can be changed into another prime (21518647454477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10759323727488 + 10759323727489.

It is an arithmetic number, because the mean of its divisors is an integer number (10759323727489).

Almost surely, 2^{21518647454977} is an apocalyptic number.

It is an amenable number.

21518647454977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21518647454977 is an equidigital number, since it uses as much as digits as its factorization.

21518647454977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 474163200, while the sum is 70.

The spelling of 21518647454977 in words is "twenty-one trillion, five hundred eighteen billion, six hundred forty-seven million, four hundred fifty-four thousand, nine hundred seventy-seven".