21937765 has 4 divisors (see below), whose sum is σ = 26325324. Its totient is φ = 17550208.

The previous prime is 21937763. The next prime is 21937771. The reversal of 21937765 is 56773912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7322436 + 14615329 = 2706^2 + 3823^2 .

It is a cyclic number.

It is not a de Polignac number, because 21937765 - 2¹ = 21937763 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21937763) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2193772 + ... + 2193781.

It is an arithmetic number, because the mean of its divisors is an integer number (6581331).

Almost surely, 2^21937765 is an apocalyptic number.

It is an amenable number.

21937765 is a deficient number, since it is larger than the sum of its proper divisors (4387559).

21937765 is an equidigital number, since it uses as much as digits as its factorization.

21937765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4387558.

The product of its digits is 79380, while the sum is 40.

The square root of 21937765 is about 4683.7767880205. The cubic root of 21937765 is about 279.9394639539.

The spelling of 21937765 in words is "twenty-one million, nine hundred thirty-seven thousand, seven hundred sixty-five".