21520331 has 8 divisors (see below), whose sum is σ = 25889280. Its totient is φ = 17475048.

The previous prime is 21520307. The next prime is 21520361. The reversal of 21520331 is 13302512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21520331 - 2¹⁴ = 21503947 is a prime.

It is a super-2 number, since 2×21520331² = 926249292699122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21520361) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80771 + ... + 81036.

It is an arithmetic number, because the mean of its divisors is an integer number (3236160).

Almost surely, 2^21520331 is an apocalyptic number.

21520331 is a deficient number, since it is larger than the sum of its proper divisors (4368949).

21520331 is a wasteful number, since it uses less digits than its factorization.

21520331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161833.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21520331 is about 4639.0010778184. The cubic root of 21520331 is about 278.1525093524.

Adding to 21520331 its reverse (13302512), we get a palindrome (34822843).

The spelling of 21520331 in words is "twenty-one million, five hundred twenty thousand, three hundred thirty-one".