21805753 has 4 divisors (see below), whose sum is σ = 22131280. Its totient is φ = 21480228.

The previous prime is 21805739. The next prime is 21805769. The reversal of 21805753 is 35750812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21805753 - 2¹³ = 21797561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21805783) 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, 162663 + ... + 162796.

It is an arithmetic number, because the mean of its divisors is an integer number (5532820).

Almost surely, 2^21805753 is an apocalyptic number.

It is an amenable number.

21805753 is a deficient number, since it is larger than the sum of its proper divisors (325527).

21805753 is an equidigital number, since it uses as much as digits as its factorization.

21805753 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325526.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21805753 is about 4669.6630499427. The cubic root of 21805753 is about 279.3768155637.

The spelling of 21805753 in words is "twenty-one million, eight hundred five thousand, seven hundred fifty-three".