21104861 has 4 divisors (see below), whose sum is σ = 21114492. Its totient is φ = 21095232.

The previous prime is 21104857. The next prime is 21104879. The reversal of 21104861 is 16840112.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 20884900 + 219961 = 4570^2 + 469^2 .

It is a cyclic number.

It is not a de Polignac number, because 21104861 - 2² = 21104857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21104851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 245 + ... + 6501.

It is an arithmetic number, because the mean of its divisors is an integer number (5278623).

Almost surely, 2^21104861 is an apocalyptic number.

It is an amenable number.

21104861 is a deficient number, since it is larger than the sum of its proper divisors (9631).

21104861 is an equidigital number, since it uses as much as digits as its factorization.

21104861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9630.

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 21104861 is about 4594.0027209396. The cubic root of 21104861 is about 276.3508673924.

Adding to 21104861 its reverse (16840112), we get a palindrome (37944973).

The spelling of 21104861 in words is "twenty-one million, one hundred four thousand, eight hundred sixty-one".