21972228 has 96 divisors (see below), whose sum is σ = 57915648. Its totient is φ = 6451200.

The previous prime is 21972217. The next prime is 21972229. The reversal of 21972228 is 82227912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21972229) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 309433 + ... + 309503.

It is an arithmetic number, because the mean of its divisors is an integer number (603288).

Almost surely, 2^21972228 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21972228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28957824).

21972228 is an abundant number, since it is smaller than the sum of its proper divisors (35943420).

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

21972228 is a wasteful number, since it uses less digits than its factorization.

21972228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173 (or 171 counting only the distinct ones).

The product of its digits is 8064, while the sum is 33.

The square root of 21972228 is about 4687.4543197774. The cubic root of 21972228 is about 280.0859769985.

The spelling of 21972228 in words is "twenty-one million, nine hundred seventy-two thousand, two hundred twenty-eight".