21516461 has 4 divisors (see below), whose sum is σ = 21528000. Its totient is φ = 21504924.

The previous prime is 21516437. The next prime is 21516487. The reversal of 21516461 is 16461512.

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 a de Polignac number, because none of the positive numbers 2^k-21516461 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21516461.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21516421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2261 + ... + 6938.

It is an arithmetic number, because the mean of its divisors is an integer number (5382000).

Almost surely, 2^21516461 is an apocalyptic number.

It is an amenable number.

21516461 is a deficient number, since it is larger than the sum of its proper divisors (11539).

21516461 is an equidigital number, since it uses as much as digits as its factorization.

21516461 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11538.

The product of its digits is 1440, while the sum is 26.

The square root of 21516461 is about 4638.5839434034. The cubic root of 21516461 is about 278.1358349690.

Adding to 21516461 its reverse (16461512), we get a palindrome (37977973).

The spelling of 21516461 in words is "twenty-one million, five hundred sixteen thousand, four hundred sixty-one".