20803721 has 4 divisors (see below), whose sum is σ = 20813892. Its totient is φ = 20793552.

The previous prime is 20803709. The next prime is 20803729. The reversal of 20803721 is 12730802.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 373321 + 20430400 = 611^2 + 4520^2 .

It is a cyclic number.

It is not a de Polignac number, because 20803721 - 2¹⁰ = 20802697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20803729) 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, 830 + ... + 6503.

It is an arithmetic number, because the mean of its divisors is an integer number (5203473).

Almost surely, 2^20803721 is an apocalyptic number.

It is an amenable number.

20803721 is a deficient number, since it is larger than the sum of its proper divisors (10171).

20803721 is an equidigital number, since it uses as much as digits as its factorization.

20803721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10170.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 20803721 is about 4561.1096237648. The cubic root of 20803721 is about 275.0301718962.

The spelling of 20803721 in words is "twenty million, eight hundred three thousand, seven hundred twenty-one".