21509141 has 2 divisors, whose sum is σ = 21509142. Its totient is φ = 21509140.

The previous prime is 21509119. The next prime is 21509143. The reversal of 21509141 is 14190512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11930116 + 9579025 = 3454^2 + 3095^2 .

It is a cyclic number.

It is not a de Polignac number, because 21509141 - 2¹⁰ = 21508117 is a prime.

Together with 21509143, 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 (21509143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10754570 + 10754571.

It is an arithmetic number, because the mean of its divisors is an integer number (10754571).

Almost surely, 2^21509141 is an apocalyptic number.

It is an amenable number.

21509141 is a deficient number, since it is larger than the sum of its proper divisors (1).

21509141 is an equidigital number, since it uses as much as digits as its factorization.

21509141 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 23.

The square root of 21509141 is about 4637.7948423793. The cubic root of 21509141 is about 278.1042903571.

Adding to 21509141 its reverse (14190512), we get a palindrome (35699653).

The spelling of 21509141 in words is "twenty-one million, five hundred nine thousand, one hundred forty-one".