21530210 has 16 divisors (see below), whose sum is σ = 41735736. Its totient is φ = 7949568.

The previous prime is 21530161. The next prime is 21530227. The reversal of 21530210 is 1203512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 18464209 + 3066001 = 4297^2 + 1751^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 82679 + ... + 82938.

Almost surely, 2^21530210 is an apocalyptic number.

21530210 is a deficient number, since it is larger than the sum of its proper divisors (20205526).

21530210 is a wasteful number, since it uses less digits than its factorization.

21530210 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165637.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21530210 is about 4640.0657322930. The cubic root of 21530210 is about 278.1950652076.

Adding to 21530210 its reverse (1203512), we get a palindrome (22733722).

The spelling of 21530210 in words is "twenty-one million, five hundred thirty thousand, two hundred ten".