21145409 has 2 divisors, whose sum is σ = 21145410. Its totient is φ = 21145408.

The previous prime is 21145403. The next prime is 21145417. The reversal of 21145409 is 90454112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11751184 + 9394225 = 3428^2 + 3065^2 .

It is a cyclic number.

It is not a de Polignac number, because 21145409 - 2⁴ = 21145393 is a prime.

It is not a weakly prime, because it can be changed into another prime (21145403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572704 + 10572705.

It is an arithmetic number, because the mean of its divisors is an integer number (10572705).

Almost surely, 2^21145409 is an apocalyptic number.

It is an amenable number.

21145409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21145409 is an equidigital number, since it uses as much as digits as its factorization.

21145409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21145409 is about 4598.4137482397. The cubic root of 21145409 is about 276.5277351196.

It can be divided in two parts, 2 and 1145409, that added together give a palindrome (1145411).

The spelling of 21145409 in words is "twenty-one million, one hundred forty-five thousand, four hundred nine".