21727218 has 32 divisors (see below), whose sum is σ = 45158400. Its totient is φ = 6961680.

The previous prime is 21727217. The next prime is 21727231. The reversal of 21727218 is 81272712.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21727213) 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, 36721 + ... + 37307.

It is an arithmetic number, because the mean of its divisors is an integer number (1411200).

Almost surely, 2^21727218 is an apocalyptic number.

21727218 is an abundant number, since it is smaller than the sum of its proper divisors (23431182).

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

21727218 is a wasteful number, since it uses less digits than its factorization.

21727218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 822.

The product of its digits is 3136, while the sum is 30.

The square root of 21727218 is about 4661.2463998377. The cubic root of 21727218 is about 279.0410134848.

It can be divided in two parts, 21727 and 218, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21727218 in words is "twenty-one million, seven hundred twenty-seven thousand, two hundred eighteen".