20821243 has 8 divisors (see below), whose sum is σ = 22757760. Its totient is φ = 18963840.

The previous prime is 20821223. The next prime is 20821249. The reversal of 20821243 is 34212802.

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

It is not a de Polignac number, because 20821243 - 2⁵ = 20821211 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20821249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19228 + ... + 20281.

It is an arithmetic number, because the mean of its divisors is an integer number (2844720).

Almost surely, 2^20821243 is an apocalyptic number.

20821243 is a deficient number, since it is larger than the sum of its proper divisors (1936517).

20821243 is a wasteful number, since it uses less digits than its factorization.

20821243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39557.

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 20821243 is about 4563.0300240082. The cubic root of 20821243 is about 275.1073652396.

The spelling of 20821243 in words is "twenty million, eight hundred twenty-one thousand, two hundred forty-three".