21123401543 has 2 divisors, whose sum is σ = 21123401544. Its totient is φ = 21123401542.

The previous prime is 21123401471. The next prime is 21123401567. The reversal of 21123401543 is 34510432112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123401543 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123401573) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561700771 + 10561700772.

It is an arithmetic number, because the mean of its divisors is an integer number (10561700772).

Almost surely, 2^21123401543 is an apocalyptic number.

21123401543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123401543 is an equidigital number, since it uses as much as digits as its factorization.

21123401543 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 26.

Adding to 21123401543 its reverse (34510432112), we get a palindrome (55633833655).

The spelling of 21123401543 in words is "twenty-one billion, one hundred twenty-three million, four hundred one thousand, five hundred forty-three".