21530020 has 12 divisors (see below), whose sum is σ = 45213084. Its totient is φ = 8612000.

The previous prime is 21530017. The next prime is 21530077. The reversal of 21530020 is 2003512.

It can be written as a sum of positive squares in 2 ways, for example, as 10810944 + 10719076 = 3288^2 + 3274^2 .

It is a super-2 number, since 2×21530020² = 927083522400800, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 538231 + ... + 538270.

It is an arithmetic number, because the mean of its divisors is an integer number (3767757).

Almost surely, 2^21530020 is an apocalyptic number.

21530020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21530020 is an abundant number, since it is smaller than the sum of its proper divisors (23683064).

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

21530020 is a wasteful number, since it uses less digits than its factorization.

21530020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1076510 (or 1076508 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 13.

The square root of 21530020 is about 4640.0452584000. The cubic root of 21530020 is about 278.1942468657.

Adding to 21530020 its reverse (2003512), we get a palindrome (23533532).

The spelling of 21530020 in words is "twenty-one million, five hundred thirty thousand, twenty".