21540473 has 2 divisors, whose sum is σ = 21540474. Its totient is φ = 21540472.

The previous prime is 21540439. The next prime is 21540529. The reversal of 21540473 is 37404512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11377129 + 10163344 = 3373^2 + 3188^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540473 - 2⁸ = 21540217 is a prime.

It is not a weakly prime, because it can be changed into another prime (21540773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770236 + 10770237.

It is an arithmetic number, because the mean of its divisors is an integer number (10770237).

Almost surely, 2^21540473 is an apocalyptic number.

It is an amenable number.

21540473 is a deficient number, since it is larger than the sum of its proper divisors (1).

21540473 is an equidigital number, since it uses as much as digits as its factorization.

21540473 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3360, while the sum is 26.

The square root of 21540473 is about 4641.1715115906. The cubic root of 21540473 is about 278.2392614388.

Adding to 21540473 its reverse (37404512), we get a palindrome (58944985).

The spelling of 21540473 in words is "twenty-one million, five hundred forty thousand, four hundred seventy-three".