21543155401 has 2 divisors, whose sum is σ = 21543155402. Its totient is φ = 21543155400.

The previous prime is 21543155369. The next prime is 21543155419. The reversal of 21543155401 is 10455134512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21148139776 + 395015625 = 145424^2 + 19875^2 .

It is a cyclic number.

It is not a de Polignac number, because 21543155401 - 2⁵ = 21543155369 is a prime.

It is not a weakly prime, because it can be changed into another prime (21543155461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771577700 + 10771577701.

It is an arithmetic number, because the mean of its divisors is an integer number (10771577701).

Almost surely, 2^21543155401 is an apocalyptic number.

It is an amenable number.

21543155401 is a deficient number, since it is larger than the sum of its proper divisors (1).

21543155401 is an equidigital number, since it uses as much as digits as its factorization.

21543155401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12000, while the sum is 31.

Adding to 21543155401 its reverse (10455134512), we get a palindrome (31998289913).

The spelling of 21543155401 in words is "twenty-one billion, five hundred forty-three million, one hundred fifty-five thousand, four hundred one".