21704261 has 2 divisors, whose sum is σ = 21704262. Its totient is φ = 21704260.

The previous prime is 21704233. The next prime is 21704279. The reversal of 21704261 is 16240712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15484225 + 6220036 = 3935^2 + 2494^2 .

It is a cyclic number.

It is not a de Polignac number, because 21704261 - 2⁶ = 21704197 is a prime.

It is a super-2 number, since 2×21704261² = 942149891112242, which contains 22 as substring.

It is a Sophie Germain 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 (21704231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852130 + 10852131.

It is an arithmetic number, because the mean of its divisors is an integer number (10852131).

Almost surely, 2^21704261 is an apocalyptic number.

It is an amenable number.

21704261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21704261 is an equidigital number, since it uses as much as digits as its factorization.

21704261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21704261 is about 4658.7832102385. The cubic root of 21704261 is about 278.9427005140.

Adding to 21704261 its reverse (16240712), we get a palindrome (37944973).

The spelling of 21704261 in words is "twenty-one million, seven hundred four thousand, two hundred sixty-one".