21030540 has 96 divisors (see below), whose sum is σ = 61641216. Its totient is φ = 5352960.

The previous prime is 21030469. The next prime is 21030551. The reversal of 21030540 is 4503012.

It is a super-2 number, since 2×21030540² = 884567225383200, which contains 22 as substring.

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

It is a congruent number.

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, 204129 + ... + 204231.

It is an arithmetic number, because the mean of its divisors is an integer number (642096).

Almost surely, 2^21030540 is an apocalyptic number.

21030540 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 21030540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30820608).

21030540 is an abundant number, since it is smaller than the sum of its proper divisors (40610676).

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

21030540 is a wasteful number, since it uses less digits than its factorization.

21030540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 239 (or 237 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 15.

The square root of 21030540 is about 4585.9066715318. The cubic root of 21030540 is about 276.0260949912.

Adding to 21030540 its reverse (4503012), we get a palindrome (25533552).

The spelling of 21030540 in words is "twenty-one million, thirty thousand, five hundred forty".