21123031843 has 2 divisors, whose sum is σ = 21123031844. Its totient is φ = 21123031842.

The previous prime is 21123031819. The next prime is 21123031849. The reversal of 21123031843 is 34813032112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123031843 is a prime.

It is not a weakly prime, because it can be changed into another prime (21123031849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561515921 + 10561515922.

It is an arithmetic number, because the mean of its divisors is an integer number (10561515922).

Almost surely, 2^21123031843 is an apocalyptic number.

21123031843 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123031843 is an equidigital number, since it uses as much as digits as its factorization.

21123031843 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 28.

Adding to 21123031843 its reverse (34813032112), we get a palindrome (55936063955).

The spelling of 21123031843 in words is "twenty-one billion, one hundred twenty-three million, thirty-one thousand, eight hundred forty-three".