21442890 has 96 divisors (see below), whose sum is σ = 62052480. Its totient is φ = 4722816.

The previous prime is 21442871. The next prime is 21442913. The reversal of 21442890 is 9824412.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 42379 + ... + 42881.

It is an arithmetic number, because the mean of its divisors is an integer number (646380).

Almost surely, 2^21442890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21442890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31026240).

21442890 is an abundant number, since it is smaller than the sum of its proper divisors (40609590).

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

21442890 is a wasteful number, since it uses less digits than its factorization.

21442890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556 (or 549 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 21442890 is about 4630.6468230691. The cubic root of 21442890 is about 277.8184640256.

The spelling of 21442890 in words is "twenty-one million, four hundred forty-two thousand, eight hundred ninety".