21555044 has 48 divisors (see below), whose sum is σ = 46878720. Its totient is φ = 8462880.

The previous prime is 21555041. The next prime is 21555067. The reversal of 21555044 is 44055512.

It is not an unprimeable number, because it can be changed into a prime (21555041) 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, 15839 + ... + 17145.

It is an arithmetic number, because the mean of its divisors is an integer number (976640).

Almost surely, 2^21555044 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 21555044, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23439360).

21555044 is an abundant number, since it is smaller than the sum of its proper divisors (25323676).

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

21555044 is a wasteful number, since it uses less digits than its factorization.

21555044 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1368 (or 1366 counting only the distinct ones).

The product of its (nonzero) digits is 4000, while the sum is 26.

The square root of 21555044 is about 4642.7410007451. The cubic root of 21555044 is about 278.3019853859.

The spelling of 21555044 in words is "twenty-one million, five hundred fifty-five thousand, forty-four".