21861005 has 4 divisors (see below), whose sum is σ = 26233212.
Its totient is φ = 17488800.
The previous prime is 21860977. The next prime is 21861013. The reversal of 21861005 is 50016812.
Adding to 21861005 its reverse (50016812), we get a palindrome (71877817).
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 12411529 + 9449476 = 3523^2 + 3074^2
It is not a de Polignac number, because 21861005 - 26 = 21860941 is a prime.
It is a super-2 number, since 2×218610052 = 955807079220050, which contains 22 as substring.
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, 2186096 + ... + 2186105.
It is an arithmetic number, because the mean of its divisors is an integer number (6558303).
Almost surely, 221861005 is an apocalyptic number.
It is an amenable number.
21861005 is a deficient number, since it is larger than the sum of its proper divisors (4372207).
21861005 is an equidigital number, since it uses as much as digits as its factorization.
21861005 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 4372206.
The product of its (nonzero) digits is 480, while the sum is 23.
The square root of 21861005 is about 4675.5753656636.
The cubic root of 21861005 is about 279.6125806948.
The spelling of 21861005 in words is "twenty-one million, eight hundred sixty-one thousand, five".