21236765 has 16 divisors (see below), whose sum is σ = 28083456. Its totient is φ = 15288000.

The previous prime is 21236753. The next prime is 21236771. The reversal of 21236765 is 56763212.

It is not a de Polignac number, because 21236765 - 2⁴ = 21236749 is a prime.

It is a super-3 number, since 3×21236765³ (a number of 23 digits) contains 333 as substring.

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

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3644 + ... + 7466.

It is an arithmetic number, because the mean of its divisors is an integer number (1755216).

Almost surely, 2^21236765 is an apocalyptic number.

It is an amenable number.

21236765 is a deficient number, since it is larger than the sum of its proper divisors (6846691).

21236765 is a wasteful number, since it uses less digits than its factorization.

21236765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3940.

The product of its digits is 15120, while the sum is 32.

The square root of 21236765 is about 4608.3364677506. The cubic root of 21236765 is about 276.9253970702.

Adding to 21236765 its reverse (56763212), we get a palindrome (77999977).

It can be divided in two parts, 2123 and 6765, that added together give a palindrome (8888).

The spelling of 21236765 in words is "twenty-one million, two hundred thirty-six thousand, seven hundred sixty-five".