20521317 has 4 divisors (see below), whose sum is σ = 27361760. Its totient is φ = 13680876.

The previous prime is 20521309. The next prime is 20521331. The reversal of 20521317 is 71312502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20521317 - 2³ = 20521309 is a prime.

It is a super-2 number, since 2×20521317² = 842248902828978, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20521293 and 20521302.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3420217 + ... + 3420222.

It is an arithmetic number, because the mean of its divisors is an integer number (6840440).

Almost surely, 2^20521317 is an apocalyptic number.

It is an amenable number.

20521317 is a deficient number, since it is larger than the sum of its proper divisors (6840443).

20521317 is an equidigital number, since it uses as much as digits as its factorization.

20521317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6840442.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 20521317 is about 4530.0460262562. The cubic root of 20521317 is about 273.7800150571.

Adding to 20521317 its reverse (71312502), we get a palindrome (91833819).

The spelling of 20521317 in words is "twenty million, five hundred twenty-one thousand, three hundred seventeen".