21138742723 has 4 divisors (see below), whose sum is σ = 24158563120. Its totient is φ = 18118922328.

The previous prime is 21138742721. The next prime is 21138742739. The reversal of 21138742723 is 32724783112.

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 21138742723 - 2¹ = 21138742721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21138742721) 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, 1509910188 + ... + 1509910201.

It is an arithmetic number, because the mean of its divisors is an integer number (6039640780).

Almost surely, 2^21138742723 is an apocalyptic number.

21138742723 is a deficient number, since it is larger than the sum of its proper divisors (3019820397).

21138742723 is an equidigital number, since it uses as much as digits as its factorization.

21138742723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3019820396.

The product of its digits is 112896, while the sum is 40.

The spelling of 21138742723 in words is "twenty-one billion, one hundred thirty-eight million, seven hundred forty-two thousand, seven hundred twenty-three".