21516784771 has 2 divisors, whose sum is σ = 21516784772. Its totient is φ = 21516784770.

The previous prime is 21516784741. The next prime is 21516784799. The reversal of 21516784771 is 17748761512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21516784771 - 2²¹ = 21514687619 is a prime.

It is not a weakly prime, because it can be changed into another prime (21516784711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758392385 + 10758392386.

It is an arithmetic number, because the mean of its divisors is an integer number (10758392386).

Almost surely, 2^21516784771 is an apocalyptic number.

21516784771 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516784771 is an equidigital number, since it uses as much as digits as its factorization.

21516784771 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 658560, while the sum is 49.

The spelling of 21516784771 in words is "twenty-one billion, five hundred sixteen million, seven hundred eighty-four thousand, seven hundred seventy-one".