21855751 has 4 divisors (see below), whose sum is σ = 22214104. Its totient is φ = 21497400.

The previous prime is 21855737. The next prime is 21855781. The reversal of 21855751 is 15755812.

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

It is a cyclic number.

It is not a de Polignac number, because 21855751 - 2⁷ = 21855623 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 (21855781) 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, 179085 + ... + 179206.

It is an arithmetic number, because the mean of its divisors is an integer number (5553526).

Almost surely, 2^21855751 is an apocalyptic number.

21855751 is a deficient number, since it is larger than the sum of its proper divisors (358353).

21855751 is an equidigital number, since it uses as much as digits as its factorization.

21855751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358352.

The product of its digits is 14000, while the sum is 34.

The square root of 21855751 is about 4675.0134759164. The cubic root of 21855751 is about 279.5901785194.

The spelling of 21855751 in words is "twenty-one million, eight hundred fifty-five thousand, seven hundred fifty-one".