21016681 has 8 divisors (see below), whose sum is σ = 24058944. Its totient is φ = 17984400.

The previous prime is 21016669. The next prime is 21016691. The reversal of 21016681 is 18661012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21016681 - 2⁵ = 21016649 is a prime.

It is a super-2 number, since 2×21016681² = 883401760511522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21016601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2766 + ... + 7048.

It is an arithmetic number, because the mean of its divisors is an integer number (3007368).

Almost surely, 2^21016681 is an apocalyptic number.

It is an amenable number.

21016681 is a deficient number, since it is larger than the sum of its proper divisors (3042263).

21016681 is an equidigital number, since it uses as much as digits as its factorization.

21016681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4991.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21016681 is about 4584.3953799820. The cubic root of 21016681 is about 275.9654484858.

Adding to 21016681 its reverse (18661012), we get a palindrome (39677693).

The spelling of 21016681 in words is "twenty-one million, sixteen thousand, six hundred eighty-one".