21813573 has 4 divisors (see below), whose sum is σ = 29084768. Its totient is φ = 14542380.

The previous prime is 21813569. The next prime is 21813619. The reversal of 21813573 is 37531812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21813573 - 2² = 21813569 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21813573.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21813503) 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, 3635593 + ... + 3635598.

It is an arithmetic number, because the mean of its divisors is an integer number (7271192).

Almost surely, 2^21813573 is an apocalyptic number.

It is an amenable number.

21813573 is a deficient number, since it is larger than the sum of its proper divisors (7271195).

21813573 is an equidigital number, since it uses as much as digits as its factorization.

21813573 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7271194.

The product of its digits is 5040, while the sum is 30.

The square root of 21813573 is about 4670.5002944010. The cubic root of 21813573 is about 279.4102083659.

The spelling of 21813573 in words is "twenty-one million, eight hundred thirteen thousand, five hundred seventy-three".