21040144 has 40 divisors (see below), whose sum is σ = 43593440. Its totient is φ = 9808128.

The previous prime is 21040139. The next prime is 21040157. The reversal of 21040144 is 44104012.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19852 + ... + 20884.

It is an arithmetic number, because the mean of its divisors is an integer number (1089836).

Almost surely, 2^21040144 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 21040144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21796720).

21040144 is an abundant number, since it is smaller than the sum of its proper divisors (22553296).

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

21040144 is a wasteful number, since it uses less digits than its factorization.

21040144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1127 (or 1121 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21040144 is about 4586.9536731910. The cubic root of 21040144 is about 276.0681061360.

Adding to 21040144 its reverse (44104012), we get a palindrome (65144156).

The spelling of 21040144 in words is "twenty-one million, forty thousand, one hundred forty-four".