21906765 has 12 divisors (see below), whose sum is σ = 37971804. Its totient is φ = 11683584.

The previous prime is 21906763. The next prime is 21906767. The reversal of 21906765 is 56760912.

It is an interprime number because it is at equal distance from previous prime (21906763) and next prime (21906767).

It can be written as a sum of positive squares in 2 ways, for example, as 16232841 + 5673924 = 4029^2 + 2382^2 .

It is not a de Polignac number, because 21906765 - 2¹ = 21906763 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906763) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 243364 + ... + 243453.

It is an arithmetic number, because the mean of its divisors is an integer number (3164317).

Almost surely, 2^21906765 is an apocalyptic number.

It is an amenable number.

21906765 is a deficient number, since it is larger than the sum of its proper divisors (16065039).

21906765 is a wasteful number, since it uses less digits than its factorization.

21906765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486828 (or 486825 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 21906765 is about 4680.4663229213. The cubic root of 21906765 is about 279.8075420641.

The spelling of 21906765 in words is "twenty-one million, nine hundred six thousand, seven hundred sixty-five".