21395261 has 2 divisors, whose sum is σ = 21395262. Its totient is φ = 21395260.

The previous prime is 21395251. The next prime is 21395291. The reversal of 21395261 is 16259312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19307236 + 2088025 = 4394^2 + 1445^2 .

It is a cyclic number.

It is not a de Polignac number, because 21395261 - 2¹⁰ = 21394237 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21395251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10697630 + 10697631.

It is an arithmetic number, because the mean of its divisors is an integer number (10697631).

Almost surely, 2^21395261 is an apocalyptic number.

It is an amenable number.

21395261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21395261 is an equidigital number, since it uses as much as digits as its factorization.

21395261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3240, while the sum is 29.

The square root of 21395261 is about 4625.5011620364. The cubic root of 21395261 is about 277.6126145206.

The spelling of 21395261 in words is "twenty-one million, three hundred ninety-five thousand, two hundred sixty-one".