21541430021 has 2 divisors, whose sum is σ = 21541430022. Its totient is φ = 21541430020.

The previous prime is 21541429957. The next prime is 21541430023. The reversal of 21541430021 is 12003414512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14022112225 + 7519317796 = 118415^2 + 86714^2 .

It is a cyclic number.

It is not a de Polignac number, because 21541430021 - 2⁶ = 21541429957 is a prime.

Together with 21541430023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21541430023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770715010 + 10770715011.

It is an arithmetic number, because the mean of its divisors is an integer number (10770715011).

Almost surely, 2^21541430021 is an apocalyptic number.

It is an amenable number.

21541430021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21541430021 is an equidigital number, since it uses as much as digits as its factorization.

21541430021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 960, while the sum is 23.

Adding to 21541430021 its reverse (12003414512), we get a palindrome (33544844533).

The spelling of 21541430021 in words is "twenty-one billion, five hundred forty-one million, four hundred thirty thousand, twenty-one".