21108455 has 4 divisors (see below), whose sum is σ = 25330152. Its totient is φ = 16886760.

The previous prime is 21108431. The next prime is 21108497. The reversal of 21108455 is 55480112.

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

It is not a de Polignac number, because 21108455 - 2¹⁶ = 21042919 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, 2110841 + ... + 2110850.

It is an arithmetic number, because the mean of its divisors is an integer number (6332538).

Almost surely, 2^21108455 is an apocalyptic number.

21108455 is a deficient number, since it is larger than the sum of its proper divisors (4221697).

21108455 is an equidigital number, since it uses as much as digits as its factorization.

21108455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4221696.

The product of its (nonzero) digits is 1600, while the sum is 26.

The square root of 21108455 is about 4594.3938664420. The cubic root of 21108455 is about 276.3665533307.

Adding to 21108455 its reverse (55480112), we get a palindrome (76588567).

The spelling of 21108455 in words is "twenty-one million, one hundred eight thousand, four hundred fifty-five".