21540317 has 2 divisors, whose sum is σ = 21540318. Its totient is φ = 21540316.

The previous prime is 21540307. The next prime is 21540341. The reversal of 21540317 is 71304512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17799961 + 3740356 = 4219^2 + 1934^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540317 - 2¹⁶ = 21474781 is a prime.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21540292 and 21540301.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21540307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770158 + 10770159.

It is an arithmetic number, because the mean of its divisors is an integer number (10770159).

Almost surely, 2^21540317 is an apocalyptic number.

It is an amenable number.

21540317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21540317 is an equidigital number, since it uses as much as digits as its factorization.

21540317 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 21540317 is about 4641.1547054585. The cubic root of 21540317 is about 278.2385897508.

Adding to 21540317 its reverse (71304512), we get a palindrome (92844829).

The spelling of 21540317 in words is "twenty-one million, five hundred forty thousand, three hundred seventeen".