21506530278913 has 2 divisors, whose sum is σ = 21506530278914. Its totient is φ = 21506530278912.

The previous prime is 21506530278911. The next prime is 21506530278929. The reversal of 21506530278913 is 31987203560512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12254816473344 + 9251713805569 = 3500688^2 + 3041663^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506530278913 - 2¹ = 21506530278911 is a prime.

Together with 21506530278911, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21506530278911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753265139456 + 10753265139457.

It is an arithmetic number, because the mean of its divisors is an integer number (10753265139457).

Almost surely, 2^{21506530278913} is an apocalyptic number.

It is an amenable number.

21506530278913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506530278913 is an equidigital number, since it uses as much as digits as its factorization.

21506530278913 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2721600, while the sum is 52.

The spelling of 21506530278913 in words is "twenty-one trillion, five hundred six billion, five hundred thirty million, two hundred seventy-eight thousand, nine hundred thirteen".