20517521 has 8 divisors (see below), whose sum is σ = 22187520. Its totient is φ = 18899008.

The previous prime is 20517503. The next prime is 20517527. The reversal of 20517521 is 12571502.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20517521 - 2⁶ = 20517457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20517527) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12041 + ... + 13638.

It is an arithmetic number, because the mean of its divisors is an integer number (2773440).

Almost surely, 2^20517521 is an apocalyptic number.

It is an amenable number.

20517521 is a deficient number, since it is larger than the sum of its proper divisors (1669999).

20517521 is a wasteful number, since it uses less digits than its factorization.

20517521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25743.

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

The square root of 20517521 is about 4529.6270265884. The cubic root of 20517521 is about 273.7631328882.

The spelling of 20517521 in words is "twenty million, five hundred seventeen thousand, five hundred twenty-one".