21516784799 has 2 divisors, whose sum is σ = 21516784800. Its totient is φ = 21516784798.

The previous prime is 21516784771. The next prime is 21516784801. The reversal of 21516784799 is 99748761512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21516784799 is a prime.

Together with 21516784801, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21516784199) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758392399 + 10758392400.

It is an arithmetic number, because the mean of its divisors is an integer number (10758392400).

Almost surely, 2^21516784799 is an apocalyptic number.

21516784799 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516784799 is an equidigital number, since it uses as much as digits as its factorization.

21516784799 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7620480, while the sum is 59.

The spelling of 21516784799 in words is "twenty-one billion, five hundred sixteen million, seven hundred eighty-four thousand, seven hundred ninety-nine".