21202440 has 128 divisors (see below), whose sum is σ = 74511360. Its totient is φ = 4725504.

The previous prime is 21202429. The next prime is 21202459. The reversal of 21202440 is 4420212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 35827 + ... + 36413.

It is an arithmetic number, because the mean of its divisors is an integer number (582120).

Almost surely, 2^21202440 is an apocalyptic number.

21202440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21202440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37255680).

21202440 is an abundant number, since it is smaller than the sum of its proper divisors (53308920).

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

21202440 is a wasteful number, since it uses less digits than its factorization.

21202440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 651 (or 647 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21202440 is about 4604.6107327330. The cubic root of 21202440 is about 276.7761183691.

Adding to 21202440 its reverse (4420212), we get a palindrome (25622652).

It can be divided in two parts, 2120 and 2440, that added together give a triangular number (4560 = T₉₅).

The spelling of 21202440 in words is "twenty-one million, two hundred two thousand, four hundred forty".