21016857 has 4 divisors (see below), whose sum is σ = 28022480. Its totient is φ = 14011236.

The previous prime is 21016837. The next prime is 21016859. The reversal of 21016857 is 75861012.

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 not a de Polignac number, because 21016857 - 2⁸ = 21016601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21016859) 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, 3502807 + ... + 3502812.

It is an arithmetic number, because the mean of its divisors is an integer number (7005620).

Almost surely, 2^21016857 is an apocalyptic number.

It is an amenable number.

21016857 is a deficient number, since it is larger than the sum of its proper divisors (7005623).

21016857 is an equidigital number, since it uses as much as digits as its factorization.

21016857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7005622.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21016857 is about 4584.4145754938. The cubic root of 21016857 is about 275.9662188229.

Adding to 21016857 its reverse (75861012), we get a palindrome (96877869).

The spelling of 21016857 in words is "twenty-one million, sixteen thousand, eight hundred fifty-seven".