21388573 has 4 divisors (see below), whose sum is σ = 22126140. Its totient is φ = 20651008.

The previous prime is 21388559. The next prime is 21388583. The reversal of 21388573 is 37588312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5212089 + 16176484 = 2283^2 + 4022^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388573 - 2⁵ = 21388541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388583) 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, 368740 + ... + 368797.

It is an arithmetic number, because the mean of its divisors is an integer number (5531535).

Almost surely, 2^21388573 is an apocalyptic number.

It is an amenable number.

21388573 is a deficient number, since it is larger than the sum of its proper divisors (737567).

21388573 is an equidigital number, since it uses as much as digits as its factorization.

21388573 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 737566.

The product of its digits is 40320, while the sum is 37.

The square root of 21388573 is about 4624.7781568417. The cubic root of 21388573 is about 277.5836849575.

The spelling of 21388573 in words is "twenty-one million, three hundred eighty-eight thousand, five hundred seventy-three".