21116651 has 4 divisors (see below), whose sum is σ = 21157704. Its totient is φ = 21075600.

The previous prime is 21116647. The next prime is 21116653. The reversal of 21116651 is 15661112.

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 21116651 - 2² = 21116647 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21116653) 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 3 ways as a sum of consecutive naturals, for example, 19745 + ... + 20786.

It is an arithmetic number, because the mean of its divisors is an integer number (5289426).

Almost surely, 2^21116651 is an apocalyptic number.

21116651 is a deficient number, since it is larger than the sum of its proper divisors (41053).

21116651 is an equidigital number, since it uses as much as digits as its factorization.

21116651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41052.

The product of its digits is 360, while the sum is 23.

The square root of 21116651 is about 4595.2857364913. The cubic root of 21116651 is about 276.4023179436.

Adding to 21116651 its reverse (15661112), we get a palindrome (36777763).

The spelling of 21116651 in words is "twenty-one million, one hundred sixteen thousand, six hundred fifty-one".