21855478 has 4 divisors (see below), whose sum is σ = 32783220. Its totient is φ = 10927738.

The previous prime is 21855439. The next prime is 21855487. The reversal of 21855478 is 87455812.

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

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21855478.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5463868 + ... + 5463871.

It is an arithmetic number, because the mean of its divisors is an integer number (8195805).

Almost surely, 2^21855478 is an apocalyptic number.

21855478 is a deficient number, since it is larger than the sum of its proper divisors (10927742).

21855478 is a wasteful number, since it uses less digits than its factorization.

21855478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10927741.

The product of its digits is 89600, while the sum is 40.

The square root of 21855478 is about 4674.9842780484. The cubic root of 21855478 is about 279.5890143951.

It can be divided in two parts, 218 and 55478, that added together give a square (55696 = 236²).

The spelling of 21855478 in words is "twenty-one million, eight hundred fifty-five thousand, four hundred seventy-eight".