21442261 has 2 divisors, whose sum is σ = 21442262. Its totient is φ = 21442260.

The previous prime is 21442243. The next prime is 21442273. The reversal of 21442261 is 16224412.

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., 13003236 + 8439025 = 3606^2 + 2905^2 .

It is a cyclic number.

It is not a de Polignac number, because 21442261 - 2⁵ = 21442229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21442361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10721130 + 10721131.

It is an arithmetic number, because the mean of its divisors is an integer number (10721131).

Almost surely, 2^21442261 is an apocalyptic number.

It is an amenable number.

21442261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21442261 is an equidigital number, since it uses as much as digits as its factorization.

21442261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 768, while the sum is 22.

The square root of 21442261 is about 4630.5789054934. The cubic root of 21442261 is about 277.8157475148.

Adding to 21442261 its reverse (16224412), we get a palindrome (37666673).

The spelling of 21442261 in words is "twenty-one million, four hundred forty-two thousand, two hundred sixty-one".