21003123243 has 4 divisors (see below), whose sum is σ = 28004164328. Its totient is φ = 14002082160.

The previous prime is 21003123209. The next prime is 21003123277. The reversal of 21003123243 is 34232130012.

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

It is an interprime number because it is at equal distance from previous prime (21003123209) and next prime (21003123277).

It is not a de Polignac number, because 21003123243 - 2⁹ = 21003122731 is a prime.

It is a super-2 number, since 2×21003123243² (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 (21003123643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3500520538 + ... + 3500520543.

It is an arithmetic number, because the mean of its divisors is an integer number (7001041082).

Almost surely, 2^21003123243 is an apocalyptic number.

21003123243 is a deficient number, since it is larger than the sum of its proper divisors (7001041085).

21003123243 is an equidigital number, since it uses as much as digits as its factorization.

21003123243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7001041084.

The product of its (nonzero) digits is 864, while the sum is 21.

Adding to 21003123243 its reverse (34232130012), we get a palindrome (55235253255).

The spelling of 21003123243 in words is "twenty-one billion, three million, one hundred twenty-three thousand, two hundred forty-three".