21078855 has 48 divisors (see below), whose sum is σ = 42479424. Its totient is φ = 9469440.

The previous prime is 21078851. The next prime is 21078857. The reversal of 21078855 is 55887012.

It is not a de Polignac number, because 21078855 - 2² = 21078851 is a prime.

It is a super-2 number, since 2×21078855² = 888636256222050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21078851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 18667 + ... + 19763.

It is an arithmetic number, because the mean of its divisors is an integer number (884988).

Almost surely, 2^21078855 is an apocalyptic number.

21078855 is an abundant number, since it is smaller than the sum of its proper divisors (21400569).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21078855 is a wasteful number, since it uses less digits than its factorization.

21078855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1176 (or 1173 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The square root of 21078855 is about 4591.1714191478. The cubic root of 21078855 is about 276.2373116481.

The spelling of 21078855 in words is "twenty-one million, seventy-eight thousand, eight hundred fifty-five".