21530331 has 12 divisors (see below), whose sum is σ = 31202808. Its totient is φ = 14305824.

The previous prime is 21530329. The next prime is 21530387. The reversal of 21530331 is 13303512.

It is not a de Polignac number, because 21530331 - 2¹ = 21530329 is a prime.

It is a super-2 number, since 2×21530331² = 927110305939122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21530321) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1005 + ... + 6638.

It is an arithmetic number, because the mean of its divisors is an integer number (2600234).

Almost surely, 2^21530331 is an apocalyptic number.

21530331 is a deficient number, since it is larger than the sum of its proper divisors (9672477).

21530331 is a wasteful number, since it uses less digits than its factorization.

21530331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7962 (or 7959 counting only the distinct ones).

The product of its (nonzero) digits is 270, while the sum is 18.

The square root of 21530331 is about 4640.0787708831. The cubic root of 21530331 is about 278.1955863597.

Adding to 21530331 its reverse (13303512), we get a palindrome (34833843).

The spelling of 21530331 in words is "twenty-one million, five hundred thirty thousand, three hundred thirty-one".