21536261 has 2 divisors, whose sum is σ = 21536262. Its totient is φ = 21536260.

The previous prime is 21536213. The next prime is 21536267. The reversal of 21536261 is 16263512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13184161 + 8352100 = 3631^2 + 2890^2 .

It is a cyclic number.

It is not a de Polignac number, because 21536261 - 2¹⁰ = 21535237 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21536261.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21536267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768130 + 10768131.

It is an arithmetic number, because the mean of its divisors is an integer number (10768131).

Almost surely, 2^21536261 is an apocalyptic number.

It is an amenable number.

21536261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21536261 is an equidigital number, since it uses as much as digits as its factorization.

21536261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 26.

The square root of 21536261 is about 4640.7177246629. The cubic root of 21536261 is about 278.2211247253.

Adding to 21536261 its reverse (16263512), we get a palindrome (37799773).

The spelling of 21536261 in words is "twenty-one million, five hundred thirty-six thousand, two hundred sixty-one".