21998205 has 24 divisors (see below), whose sum is σ = 38357280. Its totient is φ = 11662560.

The previous prime is 21998203. The next prime is 21998231. The reversal of 21998205 is 50289912.

It is not a de Polignac number, because 21998205 - 2¹ = 21998203 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21998205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21998201) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6690 + ... + 9420.

It is an arithmetic number, because the mean of its divisors is an integer number (1598220).

Almost surely, 2^21998205 is an apocalyptic number.

It is an amenable number.

21998205 is a deficient number, since it is larger than the sum of its proper divisors (16359075).

21998205 is a wasteful number, since it uses less digits than its factorization.

21998205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2921 (or 2918 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 21998205 is about 4690.2244082773. The cubic root of 21998205 is about 280.1963121604.

It can be divided in two parts, 2199 and 8205, that added together give a square (10404 = 102²).

The spelling of 21998205 in words is "twenty-one million, nine hundred ninety-eight thousand, two hundred five".