21022540 has 144 divisors (see below), whose sum is σ = 59524416. Its totient is φ = 6082560.

The previous prime is 21022517. The next prime is 21022541. The reversal of 21022540 is 4522012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21022541) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 287944 + ... + 288016.

It is an arithmetic number, because the mean of its divisors is an integer number (413364).

Almost surely, 2^21022540 is an apocalyptic number.

21022540 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 21022540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29762208).

21022540 is an abundant number, since it is smaller than the sum of its proper divisors (38501876).

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

21022540 is a wasteful number, since it uses less digits than its factorization.

21022540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128 (or 115 counting only the distinct ones).

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

The square root of 21022540 is about 4585.0343510164. The cubic root of 21022540 is about 275.9910905197.

Adding to 21022540 its reverse (4522012), we get a palindrome (25544552).

The spelling of 21022540 in words is "twenty-one million, twenty-two thousand, five hundred forty".