21447855 has 96 divisors (see below), whose sum is σ = 45581760. Its totient is φ = 9504000.

The previous prime is 21447851. The next prime is 21447859. The reversal of 21447855 is 55874412.

It is an interprime number because it is at equal distance from previous prime (21447851) and next prime (21447859).

It is not a de Polignac number, because 21447855 - 2² = 21447851 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21447851) 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 95 ways as a sum of consecutive naturals, for example, 212305 + ... + 212405.

It is an arithmetic number, because the mean of its divisors is an integer number (474810).

Almost surely, 2^21447855 is an apocalyptic number.

21447855 is an abundant number, since it is smaller than the sum of its proper divisors (24133905).

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

21447855 is a wasteful number, since it uses less digits than its factorization.

21447855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150 (or 133 counting only the distinct ones).

The product of its digits is 44800, while the sum is 36.

The square root of 21447855 is about 4631.1828942507. The cubic root of 21447855 is about 277.8399048889.

It can be divided in two parts, 2144 and 7855, that added together give a palindrome (9999).

The spelling of 21447855 in words is "twenty-one million, four hundred forty-seven thousand, eight hundred fifty-five".