20855521 has 4 divisors (see below), whose sum is σ = 21953200. Its totient is φ = 19757844.

The previous prime is 20855519. The next prime is 20855537. The reversal of 20855521 is 12555802.

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 20855521 - 2¹ = 20855519 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20855521.

It is not an unprimeable number, because it can be changed into a prime (20855501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 548811 + ... + 548848.

It is an arithmetic number, because the mean of its divisors is an integer number (5488300).

Almost surely, 2^20855521 is an apocalyptic number.

It is an amenable number.

20855521 is a deficient number, since it is larger than the sum of its proper divisors (1097679).

20855521 is a wasteful number, since it uses less digits than its factorization.

20855521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1097678.

The product of its (nonzero) digits is 4000, while the sum is 28.

The square root of 20855521 is about 4566.7845361917. The cubic root of 20855521 is about 275.2582521656.

The spelling of 20855521 in words is "twenty million, eight hundred fifty-five thousand, five hundred twenty-one".