21331155 has 16 divisors (see below), whose sum is σ = 34709760. Its totient is φ = 11183328.

The previous prime is 21331147. The next prime is 21331157. The reversal of 21331155 is 55113312.

It is not a de Polignac number, because 21331155 - 2³ = 21331147 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21331157) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11167 + ... + 12936.

It is an arithmetic number, because the mean of its divisors is an integer number (2169360).

Almost surely, 2^21331155 is an apocalyptic number.

21331155 is a deficient number, since it is larger than the sum of its proper divisors (13378605).

21331155 is a wasteful number, since it uses less digits than its factorization.

21331155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24170.

The product of its digits is 450, while the sum is 21.

The square root of 21331155 is about 4618.5663359965. The cubic root of 21331155 is about 277.3350695941.

Adding to 21331155 its reverse (55113312), we get a palindrome (76444467).

The spelling of 21331155 in words is "twenty-one million, three hundred thirty-one thousand, one hundred fifty-five".