21619205 has 4 divisors (see below), whose sum is σ = 25943052. Its totient is φ = 17295360.

The previous prime is 21619159. The next prime is 21619217. The reversal of 21619205 is 50291612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16957924 + 4661281 = 4118^2 + 2159^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21619205 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2161916 + ... + 2161925.

It is an arithmetic number, because the mean of its divisors is an integer number (6485763).

Almost surely, 2^21619205 is an apocalyptic number.

It is an amenable number.

21619205 is a deficient number, since it is larger than the sum of its proper divisors (4323847).

21619205 is an equidigital number, since it uses as much as digits as its factorization.

21619205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4323846.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21619205 is about 4649.6456854259. The cubic root of 21619205 is about 278.5778441902.

The spelling of 21619205 in words is "twenty-one million, six hundred nineteen thousand, two hundred five".