21878272 has 80 divisors (see below), whose sum is σ = 49840560. Its totient is φ = 9510912.

The previous prime is 21878257. The next prime is 21878279. The reversal of 21878272 is 27287812.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21878279) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126378 + ... + 126550.

It is an arithmetic number, because the mean of its divisors is an integer number (623007).

Almost surely, 2^21878272 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 21878272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24920280).

21878272 is an abundant number, since it is smaller than the sum of its proper divisors (27962288).

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

21878272 is a wasteful number, since it uses less digits than its factorization.

21878272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223 (or 207 counting only the distinct ones).

The product of its digits is 25088, while the sum is 37.

The square root of 21878272 is about 4677.4215119016. The cubic root of 21878272 is about 279.6861790165.

The spelling of 21878272 in words is "twenty-one million, eight hundred seventy-eight thousand, two hundred seventy-two".