20721199 has 8 divisors (see below), whose sum is σ = 21056112. Its totient is φ = 20388480.

The previous prime is 20721163. The next prime is 20721209. The reversal of 20721199 is 99112702.

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

It is a cyclic number.

It is not a de Polignac number, because 20721199 - 2¹⁷ = 20590127 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 20721199.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721599) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34647 + ... + 35239.

It is an arithmetic number, because the mean of its divisors is an integer number (2632014).

Almost surely, 2^20721199 is an apocalyptic number.

20721199 is a deficient number, since it is larger than the sum of its proper divisors (334913).

20721199 is an equidigital number, since it uses as much as digits as its factorization.

20721199 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1097.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 20721199 is about 4552.0543713800. The cubic root of 20721199 is about 274.6660364679. Note that the first 3 decimals are identical.

The spelling of 20721199 in words is "twenty million, seven hundred twenty-one thousand, one hundred ninety-nine".