21255541 has 2 divisors, whose sum is σ = 21255542. Its totient is φ = 21255540.

The previous prime is 21255529. The next prime is 21255557. The reversal of 21255541 is 14555212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19980900 + 1274641 = 4470^2 + 1129^2 .

It is a cyclic number.

It is not a de Polignac number, because 21255541 - 2¹¹ = 21253493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21255581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10627770 + 10627771.

It is an arithmetic number, because the mean of its divisors is an integer number (10627771).

Almost surely, 2^21255541 is an apocalyptic number.

It is an amenable number.

21255541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21255541 is an equidigital number, since it uses as much as digits as its factorization.

21255541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2000, while the sum is 25.

The square root of 21255541 is about 4610.3731953064. The cubic root of 21255541 is about 277.0069854486.

The spelling of 21255541 in words is "twenty-one million, two hundred fifty-five thousand, five hundred forty-one".