21225040 has 20 divisors (see below), whose sum is σ = 49348404. Its totient is φ = 8489984.

The previous prime is 21225037. The next prime is 21225041. The reversal of 21225040 is 4052212.

It can be written as a sum of positive squares in 2 ways, for example, as 6906384 + 14318656 = 2628^2 + 3784^2 .

It is a tau number, because it is divible by the number of its divisors (20).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21225041) 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, 132577 + ... + 132736.

Almost surely, 2^21225040 is an apocalyptic number.

21225040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21225040 is an abundant number, since it is smaller than the sum of its proper divisors (28123364).

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

21225040 is a wasteful number, since it uses less digits than its factorization.

21225040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265326 (or 265320 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21225040 is about 4607.0641410773. The cubic root of 21225040 is about 276.8744233929.

Adding to 21225040 its reverse (4052212), we get a palindrome (25277252).

It can be divided in two parts, 212 and 25040, that added together give a palindrome (25252).

The spelling of 21225040 in words is "twenty-one million, two hundred twenty-five thousand, forty".