21121301723 has 4 divisors (see below), whose sum is σ = 21143054808. Its totient is φ = 21099548640.

The previous prime is 21121301717. The next prime is 21121301743. The reversal of 21121301723 is 32710312112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21121301723 - 2¹⁰ = 21121300699 is a prime.

It is a super-2 number, since 2×21121301723² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121301713) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10875086 + ... + 10877027.

It is an arithmetic number, because the mean of its divisors is an integer number (5285763702).

Almost surely, 2^21121301723 is an apocalyptic number.

21121301723 is a deficient number, since it is larger than the sum of its proper divisors (21753085).

21121301723 is an equidigital number, since it uses as much as digits as its factorization.

21121301723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21753084.

The product of its (nonzero) digits is 504, while the sum is 23.

Adding to 21121301723 its reverse (32710312112), we get a palindrome (53831613835).

The spelling of 21121301723 in words is "twenty-one billion, one hundred twenty-one million, three hundred one thousand, seven hundred twenty-three".