21281024 has 36 divisors (see below), whose sum is σ = 42966924. Its totient is φ = 10518528.

The previous prime is 21281021. The next prime is 21281027. The reversal of 21281024 is 42018212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21281021) and next prime (21281027).

It can be written as a sum of positive squares in 2 ways, for example, as 15366400 + 5914624 = 3920^2 + 2432^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21280987 and 21281005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21281021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24404 + ... + 25260.

Almost surely, 2^21281024 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 21281024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21483462).

21281024 is an abundant number, since it is smaller than the sum of its proper divisors (21685900).

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

21281024 is an frugal number, since it uses more digits than its factorization.

21281024 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 970 (or 956 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 21281024 is about 4613.1360266092. The cubic root of 21281024 is about 277.1176412993.

Adding to 21281024 its reverse (42018212), we get a palindrome (63299236).

The spelling of 21281024 in words is "twenty-one million, two hundred eighty-one thousand, twenty-four".