21564090173 has 2 divisors, whose sum is σ = 21564090174. Its totient is φ = 21564090172.

The previous prime is 21564090073. The next prime is 21564090199. The reversal of 21564090173 is 37109046512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18600049924 + 2964040249 = 136382^2 + 54443^2 .

It is a cyclic number.

It is not a de Polignac number, because 21564090173 - 2¹⁸ = 21563828029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21564090073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10782045086 + 10782045087.

It is an arithmetic number, because the mean of its divisors is an integer number (10782045087).

Almost surely, 2^21564090173 is an apocalyptic number.

It is an amenable number.

21564090173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21564090173 is an equidigital number, since it uses as much as digits as its factorization.

21564090173 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 45360, while the sum is 38.

The spelling of 21564090173 in words is "twenty-one billion, five hundred sixty-four million, ninety thousand, one hundred seventy-three".