20521517 has 4 divisors (see below), whose sum is σ = 20579040. Its totient is φ = 20463996.

The previous prime is 20521507. The next prime is 20521519. The reversal of 20521517 is 71512502.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 20521517 - 2⁶ = 20521453 is a prime.

It is a super-2 number, since 2×20521517² = 842265319962578, 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 = 20521492 and 20521501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521519) 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, 28223 + ... + 28940.

It is an arithmetic number, because the mean of its divisors is an integer number (5144760).

Almost surely, 2^20521517 is an apocalyptic number.

It is an amenable number.

20521517 is a deficient number, since it is larger than the sum of its proper divisors (57523).

20521517 is an equidigital number, since it uses as much as digits as its factorization.

20521517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57522.

The product of its (nonzero) digits is 700, while the sum is 23.

The square root of 20521517 is about 4530.0681010334. The cubic root of 20521517 is about 273.7809044709.

The spelling of 20521517 in words is "twenty million, five hundred twenty-one thousand, five hundred seventeen".