21016305 has 24 divisors (see below), whose sum is σ = 36759528. Its totient is φ = 11106816.

The previous prime is 21016297. The next prime is 21016309. The reversal of 21016305 is 50361012.

It can be written as a sum of positive squares in 4 ways, for example, as 304704 + 20711601 = 552^2 + 4551^2 .

It is not a de Polignac number, because 21016305 - 2³ = 21016297 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21016309) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3019 + ... + 7151.

It is an arithmetic number, because the mean of its divisors is an integer number (1531647).

Almost surely, 2^21016305 is an apocalyptic number.

It is an amenable number.

21016305 is a deficient number, since it is larger than the sum of its proper divisors (15743223).

21016305 is a wasteful number, since it uses less digits than its factorization.

21016305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4257 (or 4254 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21016305 is about 4584.3543711192. The cubic root of 21016305 is about 275.9638027514.

Adding to 21016305 its reverse (50361012), we get a palindrome (71377317).

It can be divided in two parts, 21016 and 305, that added together give a triangular number (21321 = T₂₀₆).

The spelling of 21016305 in words is "twenty-one million, sixteen thousand, three hundred five".