21170816 has 16 divisors (see below), whose sum is σ = 42176490. Its totient is φ = 10585344.

The previous prime is 21170789. The next prime is 21170857. The reversal of 21170816 is 61807112.

It can be written as a sum of positive squares in only one way, i.e., 21160000 + 10816 = 4600^2 + 104^2 .

It is a tau number, because it is divible by the number of its divisors (16).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82571 + ... + 82826.

Almost surely, 2^21170816 is an apocalyptic number.

It is an amenable number.

21170816 is a deficient number, since it is larger than the sum of its proper divisors (21005674).

21170816 is an equidigital number, since it uses as much as digits as its factorization.

21170816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165411 (or 165399 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 26.

The square root of 21170816 is about 4601.1755019777. The cubic root of 21170816 is about 276.6384435977.

Adding to 21170816 its reverse (61807112), we get a palindrome (82977928).

The spelling of 21170816 in words is "twenty-one million, one hundred seventy thousand, eight hundred sixteen".