21566610547 has 2 divisors, whose sum is σ = 21566610548. Its totient is φ = 21566610546.

The previous prime is 21566610539. The next prime is 21566610551. The reversal of 21566610547 is 74501666512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21566610547 - 2³ = 21566610539 is a prime.

It is not a weakly prime, because it can be changed into another prime (21566610557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10783305273 + 10783305274.

It is an arithmetic number, because the mean of its divisors is an integer number (10783305274).

Almost surely, 2^21566610547 is an apocalyptic number.

21566610547 is a deficient number, since it is larger than the sum of its proper divisors (1).

21566610547 is an equidigital number, since it uses as much as digits as its factorization.

21566610547 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 302400, while the sum is 43.

The spelling of 21566610547 in words is "twenty-one billion, five hundred sixty-six million, six hundred ten thousand, five hundred forty-seven".