21481540 has 96 divisors (see below), whose sum is σ = 51819264. Its totient is φ = 7434240.

The previous prime is 21481531. The next prime is 21481549. The reversal of 21481540 is 4518412.

It is an interprime number because it is at equal distance from previous prime (21481531) and next prime (21481549).

It is a super-2 number, since 2×21481540² = 922913121543200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21481549) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 320587 + ... + 320653.

It is an arithmetic number, because the mean of its divisors is an integer number (539784).

Almost surely, 2^21481540 is an apocalyptic number.

21481540 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 21481540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25909632).

21481540 is an abundant number, since it is smaller than the sum of its proper divisors (30337724).

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

21481540 is a wasteful number, since it uses less digits than its factorization.

21481540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157 (or 155 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 25.

The square root of 21481540 is about 4634.8182272879. The cubic root of 21481540 is about 277.9852829364.

Adding to 21481540 its reverse (4518412), we get a palindrome (25999952).

The spelling of 21481540 in words is "twenty-one million, four hundred eighty-one thousand, five hundred forty".