21116855 has 4 divisors (see below), whose sum is σ = 25340232. Its totient is φ = 16893480.

The previous prime is 21116831. The next prime is 21116857. The reversal of 21116855 is 55861112.

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

It is not a de Polignac number, because 21116855 - 2¹⁸ = 20854711 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21116857) 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, 2111681 + ... + 2111690.

It is an arithmetic number, because the mean of its divisors is an integer number (6335058).

Almost surely, 2^21116855 is an apocalyptic number.

21116855 is a deficient number, since it is larger than the sum of its proper divisors (4223377).

21116855 is an equidigital number, since it uses as much as digits as its factorization.

21116855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4223376.

The product of its digits is 2400, while the sum is 29.

The square root of 21116855 is about 4595.3079330987. The cubic root of 21116855 is about 276.4032080136.

Adding to 21116855 its reverse (55861112), we get a palindrome (76977967).

The spelling of 21116855 in words is "twenty-one million, one hundred sixteen thousand, eight hundred fifty-five".