21791859 has 4 divisors (see below), whose sum is σ = 29055816. Its totient is φ = 14527904.

The previous prime is 21791843. The next prime is 21791873. The reversal of 21791859 is 95819712.

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 21791859 - 2⁴ = 21791843 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21791859.

It is not an unprimeable number, because it can be changed into a prime (21791839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3631974 + ... + 3631979.

It is an arithmetic number, because the mean of its divisors is an integer number (7263954).

Almost surely, 2^21791859 is an apocalyptic number.

21791859 is a deficient number, since it is larger than the sum of its proper divisors (7263957).

21791859 is an equidigital number, since it uses as much as digits as its factorization.

21791859 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7263956.

The product of its digits is 45360, while the sum is 42.

The square root of 21791859 is about 4668.1751252497. The cubic root of 21791859 is about 279.3174659937.

The spelling of 21791859 in words is "twenty-one million, seven hundred ninety-one thousand, eight hundred fifty-nine".