21803491 has 4 divisors (see below), whose sum is σ = 21861400. Its totient is φ = 21745584.

The previous prime is 21803479. The next prime is 21803521. The reversal of 21803491 is 19430812.

It is a happy number.

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 21803491 - 2¹¹ = 21801443 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21803191) 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, 28386 + ... + 29143.

It is an arithmetic number, because the mean of its divisors is an integer number (5465350).

Almost surely, 2^21803491 is an apocalyptic number.

21803491 is a deficient number, since it is larger than the sum of its proper divisors (57909).

21803491 is an equidigital number, since it uses as much as digits as its factorization.

21803491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57908.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21803491 is about 4669.4208420317. The cubic root of 21803491 is about 279.3671549295.

It can be divided in two parts, 2180 and 3491, that added together give a triangular number (5671 = T₁₀₆).

The spelling of 21803491 in words is "twenty-one million, eight hundred three thousand, four hundred ninety-one".