21312541 has 4 divisors (see below), whose sum is σ = 21582400. Its totient is φ = 21042684.

The previous prime is 21312539. The next prime is 21312587. The reversal of 21312541 is 14521312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21312541 - 2¹ = 21312539 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134811 + ... + 134968.

It is an arithmetic number, because the mean of its divisors is an integer number (5395600).

Almost surely, 2^21312541 is an apocalyptic number.

It is an amenable number.

21312541 is a deficient number, since it is larger than the sum of its proper divisors (269859).

21312541 is an equidigital number, since it uses as much as digits as its factorization.

21312541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269858.

The product of its digits is 240, while the sum is 19.

The square root of 21312541 is about 4616.5507687017. The cubic root of 21312541 is about 277.2543767094.

Adding to 21312541 its reverse (14521312), we get a palindrome (35833853).

The spelling of 21312541 in words is "twenty-one million, three hundred twelve thousand, five hundred forty-one".