21135540 has 48 divisors (see below), whose sum is σ = 59653440. Its totient is φ = 5591040.

The previous prime is 21135503. The next prime is 21135553. The reversal of 21135540 is 4553112.

It is a super-2 number, since 2×21135540² = 893422102183200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6516 + ... + 9204.

It is an arithmetic number, because the mean of its divisors is an integer number (1242780).

Almost surely, 2^21135540 is an apocalyptic number.

21135540 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 21135540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29826720).

21135540 is an abundant number, since it is smaller than the sum of its proper divisors (38517900).

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

21135540 is a wasteful number, since it uses less digits than its factorization.

21135540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2832 (or 2830 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21135540 is about 4597.3405355705. The cubic root of 21135540 is about 276.4847080194.

Adding to 21135540 its reverse (4553112), we get a palindrome (25688652).

The spelling of 21135540 in words is "twenty-one million, one hundred thirty-five thousand, five hundred forty".