21211530 has 64 divisors (see below), whose sum is σ = 52818048. Its totient is φ = 5448960.

The previous prime is 21211507. The next prime is 21211577. The reversal of 21211530 is 3511212.

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

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 122524 + ... + 122696.

It is an arithmetic number, because the mean of its divisors is an integer number (825282).

Almost surely, 2^21211530 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21211530, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26409024).

21211530 is an abundant number, since it is smaller than the sum of its proper divisors (31606518).

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

21211530 is a wasteful number, since it uses less digits than its factorization.

21211530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 311.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21211530 is about 4605.5976810833. The cubic root of 21211530 is about 276.8156662617.

Adding to 21211530 its reverse (3511212), we get a palindrome (24722742).

The spelling of 21211530 in words is "twenty-one million, two hundred eleven thousand, five hundred thirty".