21749867 has 4 divisors (see below), whose sum is σ = 21785736. Its totient is φ = 21714000.

The previous prime is 21749843. The next prime is 21749869. The reversal of 21749867 is 76894712.

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 21749867 - 2²⁴ = 4972651 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21749869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17009 + ... + 18242.

It is an arithmetic number, because the mean of its divisors is an integer number (5446434).

Almost surely, 2^21749867 is an apocalyptic number.

21749867 is a deficient number, since it is larger than the sum of its proper divisors (35869).

21749867 is an equidigital number, since it uses as much as digits as its factorization.

21749867 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35868.

The product of its digits is 169344, while the sum is 44.

The square root of 21749867 is about 4663.6752674259. The cubic root of 21749867 is about 279.1379396098.

The spelling of 21749867 in words is "twenty-one million, seven hundred forty-nine thousand, eight hundred sixty-seven".