21331505 has 8 divisors (see below), whose sum is σ = 27566952. Its totient is φ = 15752448.

The previous prime is 21331487. The next prime is 21331523. The reversal of 21331505 is 50513312.

It is an interprime number because it is at equal distance from previous prime (21331487) and next prime (21331523).

It can be written as a sum of positive squares in 4 ways, for example, as 2050624 + 19280881 = 1432^2 + 4391^2 .

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 21331505 - 2¹⁰ = 21330481 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 164024 + ... + 164153.

It is an arithmetic number, because the mean of its divisors is an integer number (3445869).

Almost surely, 2^21331505 is an apocalyptic number.

It is an amenable number.

21331505 is a deficient number, since it is larger than the sum of its proper divisors (6235447).

21331505 is a wasteful number, since it uses less digits than its factorization.

21331505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328195.

The product of its (nonzero) digits is 450, while the sum is 20.

The square root of 21331505 is about 4618.6042263870. The cubic root of 21331505 is about 277.3365864168.

Adding to 21331505 its reverse (50513312), we get a palindrome (71844817).

The spelling of 21331505 in words is "twenty-one million, three hundred thirty-one thousand, five hundred five".