21016765 has 32 divisors (see below), whose sum is σ = 31887360. Its totient is φ = 12916800.

The previous prime is 21016763. The next prime is 21016799. The reversal of 21016765 is 56761012.

It is not a de Polignac number, because 21016765 - 2¹ = 21016763 is a prime.

It is a super-2 number, since 2×21016765² = 883408822130450, which contains 22 as substring.

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 (21016763) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 30070 + ... + 30760.

It is an arithmetic number, because the mean of its divisors is an integer number (996480).

Almost surely, 2^21016765 is an apocalyptic number.

It is an amenable number.

21016765 is a deficient number, since it is larger than the sum of its proper divisors (10870595).

21016765 is a wasteful number, since it uses less digits than its factorization.

21016765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 793.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21016765 is about 4584.4045414863. The cubic root of 21016765 is about 275.9658161472.

Adding to 21016765 its reverse (56761012), we get a palindrome (77777777).

The spelling of 21016765 in words is "twenty-one million, sixteen thousand, seven hundred sixty-five".