21266765 has 16 divisors (see below), whose sum is σ = 27774768. Its totient is φ = 15538176.

The previous prime is 21266761. The next prime is 21266771. The reversal of 21266765 is 56766212.

It can be written as a sum of positive squares in 8 ways, for example, as 51529 + 21215236 = 227^2 + 4606^2 .

It is a cyclic number.

It is not a de Polignac number, because 21266765 - 2² = 21266761 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21266761) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4619 + ... + 7991.

It is an arithmetic number, because the mean of its divisors is an integer number (1735923).

Almost surely, 2^21266765 is an apocalyptic number.

It is an amenable number.

21266765 is a deficient number, since it is larger than the sum of its proper divisors (6508003).

21266765 is a wasteful number, since it uses less digits than its factorization.

21266765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3488.

The product of its digits is 30240, while the sum is 35.

The square root of 21266765 is about 4611.5902896940. The cubic root of 21266765 is about 277.0557347654.

It can be divided in two parts, 21 and 266765, that multiplied together give a palindrome (5602065).

The spelling of 21266765 in words is "twenty-one million, two hundred sixty-six thousand, seven hundred sixty-five".