21153540 has 48 divisors (see below), whose sum is σ = 60681600. Its totient is φ = 5502720.

The previous prime is 21153533. The next prime is 21153551. The reversal of 21153540 is 4535112.

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, 1840 + ... + 6759.

It is an arithmetic number, because the mean of its divisors is an integer number (1264200).

Almost surely, 2^21153540 is an apocalyptic number.

21153540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21153540 is an abundant number, since it is smaller than the sum of its proper divisors (39528060).

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

21153540 is a wasteful number, since it uses less digits than its factorization.

21153540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8652 (or 8650 counting only the distinct ones).

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

The square root of 21153540 is about 4599.2977724866. The cubic root of 21153540 is about 276.5631747885.

Adding to 21153540 its reverse (4535112), we get a palindrome (25688652).

It can be divided in two parts, 211535 and 40, that added together give a triangular number (211575 = T₆₅₀).

The spelling of 21153540 in words is "twenty-one million, one hundred fifty-three thousand, five hundred forty".