21504136122173 has 16 divisors (see below), whose sum is σ = 21735291006000. Its totient is φ = 21273605337600.

The previous prime is 21504136122107. The next prime is 21504136122239. The reversal of 21504136122173 is 37122163140512.

It is an interprime number because it is at equal distance from previous prime (21504136122107) and next prime (21504136122239).

It can be written as a sum of positive squares in 8 ways, for example, as 995800418404 + 20508335703769 = 997898^2 + 4528613^2 .

It is a cyclic number.

It is not a de Polignac number, because 21504136122173 - 2¹² = 21504136118077 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 (21504136122103) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 783407753 + ... + 783435201.

It is an arithmetic number, because the mean of its divisors is an integer number (1358455687875).

Almost surely, 2^{21504136122173} is an apocalyptic number.

It is an amenable number.

21504136122173 is a deficient number, since it is larger than the sum of its proper divisors (231154883827).

21504136122173 is a wasteful number, since it uses less digits than its factorization.

21504136122173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38512.

The product of its (nonzero) digits is 60480, while the sum is 38.

Adding to 21504136122173 its reverse (37122163140512), we get a palindrome (58626299262685).

The spelling of 21504136122173 in words is "twenty-one trillion, five hundred four billion, one hundred thirty-six million, one hundred twenty-two thousand, one hundred seventy-three".