20557521 has 12 divisors (see below), whose sum is σ = 29852160. Its totient is φ = 13632120.

The previous prime is 20557507. The next prime is 20557571. The reversal of 20557521 is 12575502.

It is a happy number.

It is not a de Polignac number, because 20557521 - 2⁵ = 20557489 is a prime.

It is a super-2 number, since 2×20557521² = 845223339330882, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20557571) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4261 + ... + 7698.

It is an arithmetic number, because the mean of its divisors is an integer number (2487680).

Almost surely, 2^20557521 is an apocalyptic number.

It is an amenable number.

20557521 is a deficient number, since it is larger than the sum of its proper divisors (9294639).

20557521 is a wasteful number, since it uses less digits than its factorization.

20557521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12156 (or 12153 counting only the distinct ones).

The product of its (nonzero) digits is 3500, while the sum is 27.

The square root of 20557521 is about 4534.0402512549. The cubic root of 20557521 is about 273.9409226709.

The spelling of 20557521 in words is "twenty million, five hundred fifty-seven thousand, five hundred twenty-one".