21331447 has 4 divisors (see below), whose sum is σ = 22586256. Its totient is φ = 20076640.

The previous prime is 21331399. The next prime is 21331451. The reversal of 21331447 is 74413312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21331447 - 2¹⁹ = 20807159 is a prime.

It is a super-2 number, since 2×21331447² = 910061262227618, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331477) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 627379 + ... + 627412.

It is an arithmetic number, because the mean of its divisors is an integer number (5646564).

Almost surely, 2^21331447 is an apocalyptic number.

21331447 is a deficient number, since it is larger than the sum of its proper divisors (1254809).

21331447 is a wasteful number, since it uses less digits than its factorization.

21331447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1254808.

The product of its digits is 2016, while the sum is 25.

The square root of 21331447 is about 4618.5979474295. The cubic root of 21331447 is about 277.3363350588.

Adding to 21331447 its reverse (74413312), we get a palindrome (95744759).

The spelling of 21331447 in words is "twenty-one million, three hundred thirty-one thousand, four hundred forty-seven".