21195855 has 48 divisors (see below), whose sum is σ = 39424320. Its totient is φ = 10497024.

The previous prime is 21195841. The next prime is 21195859. The reversal of 21195855 is 55859112.

It is a happy number.

It is not a de Polignac number, because 21195855 - 2⁶ = 21195791 is a prime.

Its product of digits (18000) is a multiple of the sum of its prime factors (400).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21195859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 78661 + ... + 78929.

It is an arithmetic number, because the mean of its divisors is an integer number (821340).

Almost surely, 2^21195855 is an apocalyptic number.

21195855 is a deficient number, since it is larger than the sum of its proper divisors (18228465).

21195855 is a wasteful number, since it uses less digits than its factorization.

21195855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400 (or 397 counting only the distinct ones).

The product of its digits is 18000, while the sum is 36.

The square root of 21195855 is about 4603.8956330482. The cubic root of 21195855 is about 276.7474619274.

The spelling of 21195855 in words is "twenty-one million, one hundred ninety-five thousand, eight hundred fifty-five".