21143261 has 2 divisors, whose sum is σ = 21143262. Its totient is φ = 21143260.

The previous prime is 21143251. The next prime is 21143263. The reversal of 21143261 is 16234112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19307236 + 1836025 = 4394^2 + 1355^2 .

It is a cyclic number.

It is not a de Polignac number, because 21143261 - 2⁶ = 21143197 is a prime.

Together with 21143263, 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 (21143263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10571630 + 10571631.

It is an arithmetic number, because the mean of its divisors is an integer number (10571631).

Almost surely, 2^21143261 is an apocalyptic number.

It is an amenable number.

21143261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21143261 is an equidigital number, since it uses as much as digits as its factorization.

21143261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 20.

The square root of 21143261 is about 4598.1801835074. The cubic root of 21143261 is about 276.5183713583.

Adding to 21143261 its reverse (16234112), we get a palindrome (37377373).

The spelling of 21143261 in words is "twenty-one million, one hundred forty-three thousand, two hundred sixty-one".