21813490 has 8 divisors (see below), whose sum is σ = 39264300. Its totient is φ = 8725392.

The previous prime is 21813487. The next prime is 21813497. The reversal of 21813490 is 9431812.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20729809 + 1083681 = 4553^2 + 1041^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21813497) 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, 1090665 + ... + 1090684.

Almost surely, 2^21813490 is an apocalyptic number.

21813490 is a deficient number, since it is larger than the sum of its proper divisors (17450810).

21813490 is a wasteful number, since it uses less digits than its factorization.

21813490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2181356.

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

The square root of 21813490 is about 4670.4914088348. The cubic root of 21813490 is about 279.4098539829.

It can be divided in two parts, 2181 and 3490, that added together give a triangular number (5671 = T₁₀₆).

The spelling of 21813490 in words is "twenty-one million, eight hundred thirteen thousand, four hundred ninety".