21506567573 has 2 divisors, whose sum is σ = 21506567574. Its totient is φ = 21506567572.

The previous prime is 21506567549. The next prime is 21506567623. The reversal of 21506567573 is 37576560512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15736949809 + 5769617764 = 125447^2 + 75958^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506567573 - 2²⁸ = 21238132117 is a prime.

It is a super-2 number, since 2×21506567573² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21506567503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753283786 + 10753283787.

It is an arithmetic number, because the mean of its divisors is an integer number (10753283787).

Almost surely, 2^21506567573 is an apocalyptic number.

It is an amenable number.

21506567573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506567573 is an equidigital number, since it uses as much as digits as its factorization.

21506567573 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1323000, while the sum is 47.

The spelling of 21506567573 in words is "twenty-one billion, five hundred six million, five hundred sixty-seven thousand, five hundred seventy-three".