21516413 has 4 divisors (see below), whose sum is σ = 21526560. Its totient is φ = 21506268.

The previous prime is 21516403. The next prime is 21516421. The reversal of 21516413 is 31461512.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21516413 - 2¹⁴ = 21500029 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21516403) 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, 545 + ... + 6582.

It is an arithmetic number, because the mean of its divisors is an integer number (5381640).

Almost surely, 2^21516413 is an apocalyptic number.

It is an amenable number.

21516413 is a deficient number, since it is larger than the sum of its proper divisors (10147).

21516413 is an equidigital number, since it uses as much as digits as its factorization.

21516413 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10146.

The product of its digits is 720, while the sum is 23.

The square root of 21516413 is about 4638.5787694077. The cubic root of 21516413 is about 278.1356281424.

Adding to 21516413 its reverse (31461512), we get a palindrome (52977925).

The spelling of 21516413 in words is "twenty-one million, five hundred sixteen thousand, four hundred thirteen".