21563116042609 has 2 divisors, whose sum is σ = 21563116042610. Its totient is φ = 21563116042608.

The previous prime is 21563116042607. The next prime is 21563116042621. The reversal of 21563116042609 is 90624061136512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13409218659600 + 8153897383009 = 3661860^2 + 2855503^2 .

It is a cyclic number.

It is not a de Polignac number, because 21563116042609 - 2¹ = 21563116042607 is a prime.

It is a super-2 number, since 2×21563116042609² (a number of 27 digits) contains 22 as substring.

Together with 21563116042607, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21563116042607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10781558021304 + 10781558021305.

It is an arithmetic number, because the mean of its divisors is an integer number (10781558021305).

Almost surely, 2^{21563116042609} is an apocalyptic number.

It is an amenable number.

21563116042609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21563116042609 is an equidigital number, since it uses as much as digits as its factorization.

21563116042609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 466560, while the sum is 46.

The spelling of 21563116042609 in words is "twenty-one trillion, five hundred sixty-three billion, one hundred sixteen million, forty-two thousand, six hundred nine".