21205661606527 has 2 divisors, whose sum is σ = 21205661606528. Its totient is φ = 21205661606526.

The previous prime is 21205661606513. The next prime is 21205661606533. The reversal of 21205661606527 is 72560616650212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21205661606527 - 2²³ = 21205653217919 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21205661606537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10602830803263 + 10602830803264.

It is an arithmetic number, because the mean of its divisors is an integer number (10602830803264).

Almost surely, 2^{21205661606527} is an apocalyptic number.

21205661606527 is a deficient number, since it is larger than the sum of its proper divisors (1).

21205661606527 is an equidigital number, since it uses as much as digits as its factorization.

21205661606527 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1814400, while the sum is 49.

The spelling of 21205661606527 in words is "twenty-one trillion, two hundred five billion, six hundred sixty-one million, six hundred six thousand, five hundred twenty-seven".