21701261 has 2 divisors, whose sum is σ = 21701262. Its totient is φ = 21701260.

The previous prime is 21701243. The next prime is 21701279. The reversal of 21701261 is 16210712.

It is a balanced prime because it is at equal distance from previous prime (21701243) and next prime (21701279).

It can be written as a sum of positive squares in only one way, i.e., 19758025 + 1943236 = 4445^2 + 1394^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21701261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21701201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850630 + 10850631.

It is an arithmetic number, because the mean of its divisors is an integer number (10850631).

Almost surely, 2^21701261 is an apocalyptic number.

It is an amenable number.

21701261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21701261 is an equidigital number, since it uses as much as digits as its factorization.

21701261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 21701261 is about 4658.4612266284. The cubic root of 21701261 is about 278.9298479431.

Adding to 21701261 its reverse (16210712), we get a palindrome (37911973).

The spelling of 21701261 in words is "twenty-one million, seven hundred one thousand, two hundred sixty-one".