21154520613617 has 2 divisors, whose sum is σ = 21154520613618. Its totient is φ = 21154520613616.

The previous prime is 21154520613601. The next prime is 21154520613623. The reversal of 21154520613617 is 71631602545112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13070256708961 + 8084263904656 = 3615281^2 + 2843284^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154520613617 - 2⁴ = 21154520613601 is a prime.

It is not a weakly prime, because it can be changed into another prime (21154520613697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577260306808 + 10577260306809.

It is an arithmetic number, because the mean of its divisors is an integer number (10577260306809).

Almost surely, 2^{21154520613617} is an apocalyptic number.

It is an amenable number.

21154520613617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154520613617 is an equidigital number, since it uses as much as digits as its factorization.

21154520613617 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 44.

The spelling of 21154520613617 in words is "twenty-one trillion, one hundred fifty-four billion, five hundred twenty million, six hundred thirteen thousand, six hundred seventeen".