21145261 has 2 divisors, whose sum is σ = 21145262. Its totient is φ = 21145260.

The previous prime is 21145249. The next prime is 21145301. The reversal of 21145261 is 16254112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18275625 + 2869636 = 4275^2 + 1694^2 .

It is a cyclic number.

It is not a de Polignac number, because 21145261 - 2¹⁹ = 20620973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21145961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572630 + 10572631.

It is an arithmetic number, because the mean of its divisors is an integer number (10572631).

Almost surely, 2^21145261 is an apocalyptic number.

It is an amenable number.

21145261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21145261 is an equidigital number, since it uses as much as digits as its factorization.

21145261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 22.

The square root of 21145261 is about 4598.3976557057. The cubic root of 21145261 is about 276.5270899646.

Adding to 21145261 its reverse (16254112), we get a palindrome (37399373).

The spelling of 21145261 in words is "twenty-one million, one hundred forty-five thousand, two hundred sixty-one".