20904821 has 16 divisors (see below), whose sum is σ = 24816000. Its totient is φ = 17597664.

The previous prime is 20904817. The next prime is 20904827. The reversal of 20904821 is 12840902.

It is not a de Polignac number, because 20904821 - 2² = 20904817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20904827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19721 + ... + 20753.

It is an arithmetic number, because the mean of its divisors is an integer number (1551000).

Almost surely, 2^20904821 is an apocalyptic number.

It is an amenable number.

20904821 is a deficient number, since it is larger than the sum of its proper divisors (3911179).

20904821 is an equidigital number, since it uses as much as digits as its factorization.

20904821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1113 (or 1099 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 20904821 is about 4572.1790209921. The cubic root of 20904821 is about 275.4749742036.

The spelling of 20904821 in words is "twenty million, nine hundred four thousand, eight hundred twenty-one".