21161723573 has 6 divisors (see below), whose sum is σ = 22479755106. Its totient is φ = 19916916032.

The previous prime is 21161723549. The next prime is 21161723593. The reversal of 21161723573 is 37532716112.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 2457878929 + 18703844644 = 49577^2 + 136762^2 .

It is not a de Polignac number, because 21161723573 - 2⁶ = 21161723509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21161723503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36611690 + ... + 36612267.

It is an arithmetic number, because the mean of its divisors is an integer number (3746625851).

Almost surely, 2^21161723573 is an apocalyptic number.

It is an amenable number.

21161723573 is a deficient number, since it is larger than the sum of its proper divisors (1318031533).

21161723573 is an equidigital number, since it uses as much as digits as its factorization.

21161723573 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73223991 (or 73223974 counting only the distinct ones).

The product of its digits is 52920, while the sum is 38.

The spelling of 21161723573 in words is "twenty-one billion, one hundred sixty-one million, seven hundred twenty-three thousand, five hundred seventy-three".