21313481 has 18 divisors (see below), whose sum is σ = 25646922. Its totient is φ = 17650080.

The previous prime is 21313469. The next prime is 21313483. The reversal of 21313481 is 18431312.

It can be written as a sum of positive squares in only one way, i.e., 12996025 + 8317456 = 3605^2 + 2884^2 .

It is not a de Polignac number, because 21313481 - 2¹⁰ = 21312457 is a prime.

It is a super-2 number, since 2×21313481² = 908528944674722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313483) by changing a digit.

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 17 ways as a sum of consecutive naturals, for example, 206876 + ... + 206978.

It is an arithmetic number, because the mean of its divisors is an integer number (1424829).

Almost surely, 2^21313481 is an apocalyptic number.

It is an amenable number.

21313481 is a deficient number, since it is larger than the sum of its proper divisors (4333441).

21313481 is an equidigital number, since it uses as much as digits as its factorization.

21313481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261 (or 151 counting only the distinct ones).

The product of its digits is 576, while the sum is 23.

The square root of 21313481 is about 4616.6525751891. The cubic root of 21313481 is about 277.2584527959.

Adding to 21313481 its reverse (18431312), we get a palindrome (39744793).

The spelling of 21313481 in words is "twenty-one million, three hundred thirteen thousand, four hundred eighty-one".